physicalean- research 2022

EL-LIETHY ET AL. 5 of 10

3.2 | Determination of E. coli, Salmonella, and Furthermore, sink drains in hospitals receive huge amounts of micro-
Listeria species in the natural biofilm samples organisms from hands and mouth washing and cleaning some medical
matters with or without using detergents. Moore et al. (2002) con-
About 60% of pathogenic microorganisms are involved in the biofilm firmed that the hospitals sink drains are usually refuge for both patho-
that presents in drainage pipes, hence research into the development genic and nonpathogenic microorganisms and also considered as the
of biofilm communities, their cellular organization, and composition core sources of contamination. In this work, the average counts of
become necessary to evaluate (Cooper, 2011). Consequently, in any E. coli have fluctuated between 1.1 × 103 CFU/10 cm2 (laboratory
sanitation and hygienic programs, several attempts are needed to biofilm samples) and 3.6 × 106 CFU/10 cm2 (kitchen biofilm samples)
avoid and control pathogenic contamination for public health, and (Figure 2). Moreover, a few research confirmed that the presence of
these can be supported by the assessment of fomite contamination as E. coli in natural biofilm (Juhna et al., 2007; Maes et al., 2019).
an indicator for improvement of household sanitation (Sinclair & Hemdan et al. (2015) found that the average of E. coli counts in sink
Gerba, 2011). Hence, the present work was focused on providing data drainage pipe biofilm samples was 8.8 × 104 CFU/10 cm2. Meanwhile,
on detection, determination, and identification of E. coli, Salmonella, household fomites have been observed to contribute to the dissemi-
and Listeria spp. in the natural biofilm samples grown on plastic pipe- nation of harmful bacteria (Stephens et al., 2019). Since several micro-
lines of different domestic sink drains. In this research, E. coli, Salmo- organisms can cause contaminations at minimal doses due to which
nella spp. and the most clinical relevant L. monocytogenes beside L. they can survive from hours to some weeks on the humid surfaces of
ivanovii and L. innocua isolates were detected in the all-natural biofilm kitchen and bathroom (Reynolds, Watt, Boone, & Gerba, 2005; Sin-
samples. The E. coli counts were higher than Salmonella, and Listeria clair, Choi, Riley, & Gerba, 2008). The gained results disclosed that the
counts in all biofilm samples (Figure 2). Rusin, Orosz-Coughlin, and average Salmonella counts in all collected biofilm samples were ranged
Gerba (1998) found that there were more E. coli and heterogeneous between 4.4 × 102 and 5.8 × 105 CFU/10 cm2, and the maximum Sal-
bacteria in places that were wet or regularly touched by human hands monella counts were noted in the hospital and kitchen drainage pipes
(kitchen faucet handles and kitchen sinks). The three counts of poten- samples (Figure 2). These results are following Hemdan et al. (2015),
tial pathogens were the highest biofilm samples in the kitchen, who found that Salmonella species were the most dominant in kitchen
followed by biofilm samples in the hospital. The three potential patho- drainage pipes biofilm samples. This may be due to Salmonella is envi-
gens counts were the highest in the kitchen biofilm samples, followed ronmentally persistent pathogens capable of forming the biofilm on
by in hospital biofilm samples. This may be due to raw vegetables, different surfaces under different environmental conditions and may
meats, and chicken; besides, the dishes containing cooked food resi- act as continuous sources of food contamination (Hemdan
due might harbor natural flora and some pathogenic microorganisms et al., 2019). In addition to that, Salmonella can form biofilm on plastics
are directly washing in the kitchen sink (El-Liethy et al., 2018). materials (Momba & Kaleni, 2002). Moreover, it can be considered
possible found in water supplies due to its ability to colonize surfaces
F I G U R E 2 Log10 counts of E. coli, Salmonella, and Listeria species and replicate in the biofilm of distribution system pipes and other
in the natural biofilm samples harvested from different drainage pipes micro-inhabitants (Hemdan et al., 2019). In the present study, the
Two-way analysis of variance between three tested bacterial species averages log counts of Listeria species were ranged between 102 and
statuses show that ns: discloses nonsignificance; * indicates low 104 CFU/10 cm2. The presence of Listeria spp. in kitchen and hospital
correlation (p ≤ .05), and *** discloses high correlation (p ≤ .0001). At drainage pipe biofilm samples was high compared with the other two
the same time, the statistical result for the source of variation reveals samples, and these may be due to the washing of contaminated vege-
that there is a strong correlation between the source of biofilm with tables and fruits which irrigated by insufficiently treated wastewater
significance (p ≤ .0001) that can provide a source of nonpathogenic and pathogenic microbes
(Hemdan et al., 2019). Also, Berger et al. (2010) found that the kitchen
as well-known that food items have been a reservoir for pathogenic
bacteria. Similarly, several studies have identified sink drains in the
hospital as possible sources of infections (Hemdan, 2015; Moore
et al., 2002). In the present study, it can be cleared that the biofilm
samples collected from laboratory, and hospital sink drainage pipes
have numerous of pathogenic (e.g. Salmonella and Listeria spp.) and
nonpathogenic (E. coli) microorganisms. Also, Hung and Hender-
son (2009) observed that biofilm-associated with medical and labora-
tory surfaces are often derived from the skin microflora. From
statistical analysis it was concluded that there is no significant correla-
tion between the three selected potential pathogens in lab biofilm
samples. While, there is low correlation (p ≤ .05) between the three
selected microorganisms in hospital biofilm samples. Moreover, there
is high significant correlation (p ≤ .0001) between the three selected

6 of 10 EL-LIETHY ET AL.

microorganisms in both kitchen and bathroom biofilm samples. On the 71 carbon sources including sugars, carboxylic acids, amino acids and
other hand, there is high significant correlation with significance peptides and 23 of chemical tests including pH, NaCl, and other chemical
(p ≤ .0001) between the biofilm sources with each other (Figure 2). tests. The BIOLOG test is depending on the oxidation of tetrazolium
redox dye for positive reaction (Franco-Duarte et al., 2019).
3.2.1 | Confirmation of bacterial isolates using
Biolog GEN III In this study, 80 out of 122 (65.5%) isolates were confirmed as Sal-
monella spp., which isolated from biofilm samples of sink drainage pipes,
Conventional confirmatory tests of bacterial isolates depending on mor- where 43 out of 60 suspected salmonella isolates from biofilm samples
phological identification followed by biochemical tests, then antisera collected from kitchen sink drainage pipes, 13 out of 20 isolates from
identification, are time-consuming take from 3 to 7 days and also labori- the bathroom biofilm samples, 17 out of 26 isolates from lab. Biofilm
ous (Chojniak et al., 2015). Recently, excessive attentions toward use of samples and 7 out of 16 isolates from biofilm samples collected from
BIOLOG as a rapid tool to identify and characterize microbes including hospital sink drainage pipes (Table 2). Salmonella isolates were con-
bacteria, yeasts, and fungi and to study their metabolic fingerprints (Al- firmed utilizing the following carbon sources and chemical substrates;
Dhabaan & Bakhali, 2017). BIOLOG GEN III is generally utilized for grown in 5 and 6 pH, 1 and 4% NaCl, inosine, 1% sodium lactate, fusidic
microbial communities' analysis based on physiological profiles that are acid, glycerol, D-glucose 6-PO4, D-fructose 6-PO4, D-aspartic acid,
able to provide insight into microbial roles in changing ecosystems D-serine, troleandomycin, rifamycin SV, L-aspartic acid, L-serine, linco-
(Chojniak et al., 2015; El-Liethy et al., 2018). In this study, E. coli, Salmo- mycin, Guanidine HCL, Niaproof 4, D-glucuronic acid, mucic acid,
nella, and Listeria biofilm cells, which isolated from different biofilm sam- D-scchric acid, vancomycin, tetrazolium violet and blue, P-hydroxy-
ples, were verified and identified using BIOLOG. In which 77 out of phenylacetic acid, L-lactic acid, citric acid, L-malic acid, lithium chloride,
122 (63.1%) isolates were confirmed as E. coli that isolated from biofilm γ-amino-butryric acid, propionic acid, and sodium butyrate (Table 3).
samples collected from sink drainage pipes, while, 37 out of 60 (61.6%)
isolates from the biofilm samples that collected from kitchen sink drain- Our results showed that 76 out of 122 (62.2%) presumptive Listeria
age pipes, 16 out of 20 (80%) isolates from the bathroom biofilm sam- isolates were confirmed as Listeria which isolated from biofilm samples
ples, 15 out of 26 (57.6%) isolates from the lab. Biofilm samples, and of sink drainage pipes, where 39 out of 60 (65%) isolates from kitchen
9 out of 16 (56.2%) isolates from biofilm samples of hospital sink drain- biofilm samples, 14 out of 20 (70%) isolates from biofilm samples of
age pipes (Table 2). The metabolic fingerprints of bacterial isolates are bathroom, 12 out of 26 (46%) isolates from biofilm samples from lab sink
playing a significant key in biofilm formation and giving full information drainage pipes and 11 out of 16 (68.7%) isolates from hospital sink drain-
about their behavior and metabolic activities (Hemdan et al., 2019). age pipes (Table 3). Listeria isolates were confirmed utilizing the following
Table 3 illustrates the metabolic fingerprints of E. coli, whereas E. coli carbon sources and chemical substrates; D-Maltose, D-Trehalose, D-
was able to grow at 5 and 6 pH and also in 1 and 4% NaCl. Additionally, Celobiose, Gentiobiose, grown at pH 5 and 6, D-Sallin, growing at 1, 4,
E. coli gives positive reaction with the following carbon sources and and 8% of NaCl, A-D-glucose, D-mannose, D-fructose, 1% sodium lac-
chemical substrates; Inosine, 1% sodium lactate, fusidic acid, glycerol, tate, serine, guanidine HCl, Tetrazolium violet, nalidixic acid, lithium chlo-
D-glucose 6- PO4, D-fructose 6-PO4, troleandomycin, rifamycin SV, ride, potassium tellurte, aztreonam, and sodium butyrate (Table 3).
L-lanine, L-spartic cid, L-serine, lincomycin, guanidine HCl, Niaproof
4, D-galacturonic, D-gluconic acid, vancomycin, tetrazolium violet and 3.2.2 | Confirmation of bacterial isolates
blue, L-lactic acid, L-malic acid, and sodium butyrate (Table 3). BIOLOG using PCR
is a quick and standard technique for verification microbe by utilizing
In the last few decades, molecular techniques are extensively used in
bacterial confirmation and documentation (Ina´Cio, Flores, &

T A B L E 2 Number and percentage of bacterial biofilm isolates isolated from different sink drainage pipes confirmed by Biolog GEN III
and PCR

E. coli Salmonella spp. Listeria spp.

GEN III PCR GEN III PCR GEN III PCR

Biofilm samples (number) + % + % +% + % +% + %

Kitchen (60) 37 61.6 49 81.6 43 71.6 52 86.6 39 65 51 85

Bathroom (20) 16 80 18 90 13 65 20 100 14 70 18 90

Laboratories (26) 15 57.6 21 80.7 17 65.3 23 88.4 12 46.1 20 76.9

Hospital (16) 9 52.2 13 81.2 7 43.7 12 75 11 68.7 15 93.7

Total (122) 77 63.1 101 82.7 80 65.5 107 87.7 76 62.2 104 85.2

Abbreviation: PCR, polymerase chain reaction.

EL-LIETHY ET AL.

T A B L E 3 The metabolic fingerprints of E. coli (S1), Salmonella (S2), and Listeria (S3) isolates using BIOLOG GEN III

Results Results Results Results

Properties S1 S2 S3 Properties S1 S2 S3 Properties S1 S2 S3 Properties S1 S2 S3

Negative ontrol − − − Α-D-glucose −/+ −/+ + Gelatin − − − P-hydroxy-phenylacetic acid − + −

Dextrin −/+ −/+ −/+ D-mannose −/+ −/+ + Glycyl-L-proline −/+ −/+ − Methyl pyruvate −/+ −/+ −

D-maltose −/+ −/+ + D-fructose −/+ −/+ + L-alanine + −/+ − D-lactic acid methyl ester −−−

D-trehalose −/+ −/+ + D-galactose −/+ −/+ − L-arginine −/+ − − L-lactic acid ++−

D-cellobiose − − + 3 methyl glucose − − − L-aspartic acid + + − Citric acid −+ −

Gentiobiose − − + D-fucose − − − L-glutamic acid −/+ −/+ − Α-keto-glutaric acid −−−

Sucrose − − − L-fucose −/+ −/+ − L-histidine − −/+ − D-malic acid −/+ − −

D-turanose − − − L-rhamnose −/+ −/+ −/+ L-pyroglutamic acid − − − L-malic acid ++−

Stachyose − − − Inosine + + −/+ L-serine + + − Bromo-succinic acid −/+ −/+ −

Positive control + + + 1% sodium lactate + + + Lincomycin + + − Nalidixic acid −−+

pH 6 + + + Fusidic acid + + − Guanidine HCl + + + Lithium chloride −/+ + +

pH 5 + + + Serine −/+ −/+ + Niaproof 4 + + − Potassium tellurite −/+ −/+ +

D-raffinose −/+ −/+ − D-sorbitol + −/+ − Pecin − − − Tween 40 − −/+ −

α-D-lactose −/+ − −/+ D-mannitol −/+ −/+ − D-galacturonic + − − γ-amino-butryric acid −+ −

D-melibiose −/+ −/+ − D-arabitol − − −/+ L-galactonic acid lactone −/+ − − α-hydroxy-butyric acid −/+ −/+ −

β-methyl-D-glucoside −/+ −/+ −/+ Myo-inositol − −/+ − D-gluconic acid + + − β-hydroxy-D,L-butyric acid − − −

D-salicin − − + Glycerol + + −/+ D-glucuronic acid + + − Α-keto-butyric acid −/+ −/+ −/+

N-acetyl-D-glucosamine −/+ −/+ −/+ D-glucose 6-PO4 + + − Glucuronamide −/+ −/+ − Acetoacetic acid −− −/+
Propionic acid −/+ + −
N-actyl-β-D-mannosamine −/+ + −/+ D-fructose 6-PO4 + + − Mucic acid −/+ + − Acetic acid −/+ + −

N-actyl-D-galactosamine −/+ −/+ − D-aspartic acid − + − Quinic acid − −/+ −

N-acetyl neuraminic acid −/+ + − D-serine −/+ + − D-Saccharic acid −/+ + − Formic acid −−−

1% NaCl + + + Troleandomycin + + − Vancomycin + + −/+ Aztreonam −/+ −/+ +

4% NaCl + −/+ + Rifamycin SV + + − Tetrazolium violet + + + Sodium butyrate +++

8% NaCl −/+ −/+ + Minocycline −/+ −/+ − Tetrazolium blue + + −/+ Sodium bromate −/+ −/+ −/+

Note: +, positive; −, negative; −/+, intermediate.

7 of 10

8 of 10 EL-LIETHY ET AL.

Martins, 2008). PCR is beneficial, fast, and easy technique for the Salmonella, and Listeria biofilm cells using BIOLOG were 57.6, 65.3,
identification of microbial isolates especially bacterial threats (Franco- and 46.1%, respectively. While using PCR, the results were 80.7, 88.4,
Duarte et al., 2019). Detailed PCR primers have been engaged to and 76.9%, respectively. Also bacterial isolates from hospital biofilm,
approve the presence or absence of target microbes and also used for results found that the accuracy percentage for confirmation of E. coli,
the identification of these microbes (Spilker, Coenye, Vandamme, & Salmonella, and Listeria biofilm cells using BIOLOG were 52.2, 43.7,
Lipuma, 2004). Molecular typing assesses shown that bacterium is and 68.7%, respectively. While using PCR, the results were 81.2,
capable of surviving for months and even years deeply embedded in 75, and 93.7%, respectively. The obtained results were compatible
biofilm matrices, and work has shown that the bacterium can persist with Morgan, Boyette, Goforth, Sperry, and Greene (2009) who sug-
in human feces or fecally derived material outside the human host, on gest that PCR provides more accurate identification of typical bacteria
inorganic substrates, such as wood or metal and in both handled and than the BIOLOG system. In addition to that, the genotypic character-
unregulated water (Cooper, 2011). In the present study, 122 E. coli ization of bacteria using PCR is advantageous when compared with
biofilm isolates (60 from the kitchen, 20 from the bathroom, 26 from phenotypic methods by using BIOLOG. Moreover, the phenotypic
lab and 16 from hospital sink drainage pipes) were confirmed and require a prolonged cultivation period for suspected bacteria and pure
identified using PCR with specific primer. The result revealed in Table 2 bacterial cultures for various biochemical assays (Järvinen
demonstrated that the number of positive E. coli isolates was 49 out of et al., 2009). The phenotypic investigation might be used as a trial
60 (81.6%) isolates from kitchen biofilm samples, 18 out of 20 (90%) examination; nevertheless, using PCR is more accurate and should be
isolates from bathroom biofilm samples, 21 out of 26 (80.7%) isolates used as a confirmatory tool for isolates identification (Moraes
from lab biofilm samples, and 13 out of 16 (81.2%) isolates from hospi- et al., 2013). The number of the confirmed isolates using BIOLOG was
tal biofilm samples. The results of this study reported that 122 Salmo- lower than that of the PCR; therefore, PCR is considered more accu-
nella biofilm isolates (60 from the kitchen, 20 from the bathroom, rate for the confirmation of bacterial isolates than the phenotypic
26 from lab and 16 from hospital sink drainage pipes) were confirmed method using BIOLOG. The high accuracy of PCR is returning to that
and identified using PCR with specific primer. Results tabulated in the PCR is targeting the nucleic acids of bacteria, but BIOLOG
Table 2, disclosed that the number of positive Salmonella isolates was depends on metabolic activities of the bacterial isolates. Therefore, it
as following; 52 out of 60 (86.6%) isolates from kitchen biofilm samples, can be concluded that, the PCR method has superior hand over
20 out of 20 (100%) isolates from bathroom biofilm sample, 23 out of BIOLOG identification (Hemdan et al., 2019; Janda & Abbott, 2007).
26 (88.4%) isolates from lab. Biofilm samples and 12 out of 16 (75%)
isolates from hospital biofilm samples. The results of Listeria biofilm iso- 4 | CONCLUSIONS
lates are given in Table 3 and explained that the number of positive
Listeria isolates was as follows; 51 out of 60 (85%) isolates from kitchen The natural biofilm collected from kitchen, bathroom, laboratory, and
biofilm samples, 18 out of 20 (90%) isolates from bathroom biofilm, hospital sink drainage pipes is considered the most crucial source for
20 out of 26 (76.9%) isolates from lab biofilm and 15 out of 16 (93.7%) the dissemination of nonpathogenic and pathogenic microorganisms
isolates from hospital biofilm samples. in the environmental surroundings and playing a vital role in the trans-
amination of the infection to humankind. Four different sources of
In ecological studies combination between genetic methods PCR natural biofilm (kitchen, bathroom, laboratory, and hospital sink drain-
as genotypic and phenotypic analysis by BIOLOG System, that allows age pipes) contained E. coli, Salmonella, and Listeria species. Likewise,
differentiating a large number of isolates and thus contributes to the E. coli cell densities in all examined biofilm samples were higher than
selection of the biotypes, which could be used as commercial starters the other two pathogens (Salmonella and Listeria spp.). The most sub-
(Cagno et al., 2010). From the obtained results in Table 2, it can be stantial numbers of bacterial pathogens were discovered in biofilm
found that the accuracy percentage for confirmation of bacterial iso- samples from the kitchen, followed by biofilm samples from the hospi-
lates using PCR were more reliable than BIOLOG. In a study con- tal. As a confirmatory test for the bacterial isolates, PCR was signifi-
ducted by Moraes, Perin, Júnior, and Nero (2013) mentioned that, the cantly more effective than the BIOLOG. Moreover, the biochemical
reliability of PCR technique target-specific genera and species is evaluation of pathogen-specific isolation by BIOLOG is only a useful
closed to be 100% while, the reliability of BIOLOG is ranged between tool for providing information to pathogenic bacterial cells on the
74 and 99.9% (Moraes et al., 2013). Where, the results demonstrated development of biofilms, age, and physiological characteristics. It can
that the accuracy percentage for confirmation of E. coli, Salmonella, be concluded that drains banks are a haven for opportunistic and
and Listeria isolates using BIOLOG were 61.6, 71.6, and 65%, respec- harmful microorganisms that pose a danger to humans, especially the
tively. Nevertheless by using PCR, the results were 81.6, 86.6, and elderly and low-immune people.
85%, respectively in bacterial isolates from kitchen biofilm. In case of
bacterial isolates from bathroom biofilm, the results found that the ACKNOWLEDGMENTS
accuracy percentage for confirmation of E. coli, Salmonella and Listeria The authors are grateful and thankful to Science and Technology
biofilm isolates using BIOLOG were 80, 65 and 70%, respectively. But Development Fund (STDF), Scientific Research Academy, Egypt for
using PCR, the results were 90, 100, and 90%, respectively. Con- their financial support this work under project number 15031.
cerning bacterial isolates isolated from the laboratory biofilm, results
showed that the accuracy percentages for confirmation of E. coli,

EL-LIETHY ET AL. 9 of 10

CONFLICT OF INTERESTS Ecologica Sinica, 38(5), 334–338. https://doi.org/10.1016/j.chnaes.
2018.01.011
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El-Senousy, W. M. (2015). Antibiotic susceptibility of Shiga toxin Pro-
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Infection Prevention in Practice 4 (2022) 100209

Available online at www.sciencedirect.com

Infection Prevention in Practice

journal homepage: www.elsevier.com/locate/ipip

Outbreak Report

Role of the environment in transmission of Gram-
negative bacteria in two consecutive outbreaks in a
haematology-oncology department

W.C. van der Zwet a,*, I.E.J. Nijsen a, C. Jamin a, L.B. van Alphen a,
C.J.H. von Wintersdorff a, A.M.P. Demandt b, P.H.M. Savelkoul a

a Dept. Medical Microbiology, Maastricht University Medical Center, Maastricht, the Netherlands
b Dept. Haematology, Maastricht University Medical Center, Maastricht, the Netherlands

ARTICLE INFO SUMMARY

Article history: In 2019e2020, two subsequent outbreaks caused by phenotypically identical ESBL-
Received 19 October 2021 producing Enterobacter cloacae and multi-drug-resistant (MDR) Pseudomonas putida
Accepted 9 February 2022 were detected in respectively 15 and 9 patients of the haematology-oncology department.
Available online 25 February Both bacterial species were resistant to piperacillin-tazobactam, used empirically in
2022 (neutropenic) sepsis in our hospital, and ciprofloxacin, used prophylactically in selective
digestive decontamination for haematology patients. The E. cloacae outbreak was iden-
Keywords: tified in clinical cultures of blood and urine. Despite intensified infection control meas-
Water points ures, new cases were found in weekly point-prevalence screening cultures. Environmental
Gram-negative bacteria samples of sinks and shower drains appeared positive in 18.1%. To diminish the environ-
Nosocomial infection mental contamination burden, all siphons of sinks were replaced, and disinfection of sinks
and shower drains was intensified using chlorine and soda on a daily basis. Replacement of
shower drains was not possible. The outbreak of P. putida remained limited to rectal
cultures only, and disappeared spontaneously without interventions. During both out-
breaks, multiple strains of the incriminated bacterium were found simultaneously (dem-
onstrated by Amplified-Fragment Length Polymorphism and/or Whole-Genome Multi-locus
Sequencing Typing) in patients as well as the environment. It was experimentally shown
that a biofilm on the toilet edge may act as a source for nosocomial transmission of Gram-
negative bacteria. In conclusion, the drainage system of the hospital is an important
reservoir of MDR bacteria, threatening the admitted patients. In existing hospitals, bio-
films in the drainage systems cannot be removed. Therefore, it is important that in (re)
building plans for hospitals a plan for prevention of nosocomial transmission from envi-
ronment to patients is incorporated.

ª 2022 The Authors. Published by Elsevier Ltd
on behalf of The Healthcare Infection Society. This is an open access article

under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Introduction

* Corresponding author. In recent years, many studies have demonstrated that sink
E-mail address: [email protected] (W.C. van der Zwet). drains, shower drains and toilets in hospitals can serve as a

https://doi.org/10.1016/j.infpip.2022.100209
2590-0889/ª 2022 The Authors. Published by Elsevier Ltd on behalf of The Healthcare Infection Society. This is an open access article
under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

2 W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209

reservoir of Gram-negative bacterial infections in patients We describe two subsequent outbreaks in 2019e2020 caused
[1e3]. These bacteria reside in biofilms in and on water related by ESBL-producing Enterobacter cloacae and multi drug-
devices, which are refractory to disinfection. Bacteria in the resistant Pseudomonas putida in the haematology-oncology
biofilm of drainage systems are under a prolonged antibiotic ward of our hospital, which were related to contaminated
selective pressure, because antibiotics in faeces and urine of water points. Both bacterial species were resistant to the
patients are absorbed by the biofilm [4]. Within these biofilms, antibiotics used for selective digestive decontamination (SDD),
containing several bacterial species, acquired mobile resist- which is used to prevent systemic Gram-negative infection in
ance elements are frequently transferred, resulting in highly neutropenic haematology patients, and also to the empirical
antibiotic therapy for neutropenic fever.
resistant microorganisms, such as extended-spectrum b-lac-
The E. cloacae outbreak involved 15 patients (13 haema-
tamase and carbapenemase-producing Enterobacterales and tology and two oncology), whom were infected or colonized
Pseudomonas species [5,6]. with a phenotypically identical strain (Figure 1), which proved
to consist of several genotypes, found in both patients and the
Highly resistant, (as well as antibiotic susceptible), bacteria environment. Eventually, a bundle of several interventions,
from biofilms can be transmitted to patients directly or indi- including replacement of siphons and intensive disinfection
rectly via droplets, and go on to cause infections [7]. Fur- schemes resulted in the termination of this outbreak. The
thermore, there have been a few reports of transmission via P. putida outbreak occurred one year later and involved nine
aerosols, but these remain a minority [8]. This transmission haematology patients (asymptomatic rectal colonization only).
results in a serious threat to patients, especially critically-ill This outbreak was also multi-clonal and involved patients and
patients and immunocompromised hosts, leading to sub- waterpoints, but this ended without interventions.
stantial morbidity and mortality, because treatment options are
limited. Most Gram-negative healthcare-associated waterborne Methods and materials
infections go undetected, unless they occur in outbreaks [2].
Description of water points on the haematology-
In Gram-negative nosocomial outbreaks, isolates found in oncology department
patients and water-points can be identical, but the direction of
transmission is usually unclear (water-point contamination All single and four-person rooms contain a separate sanitary
originates from waste-water from the patient, or opposite room containing a sink, shower and toilet. The two-person
direction). Therefore, the microbiomes of patients and water- rooms have a sanitary room with a sink and toilet. For these
points seem to be a continuum [9]. rooms; two extra shower rooms are created on the corridor of
the ward (Figure 2). The sinks are situated directly below the
Usually, biofilms contain several bacterial species. The outlet with a siphon. The shower drains are situated in such a
complete removal of biofilms from drains is often not possible, way that patients do not stand on it. Before and during the
because they extend into the deeper parts of the water system, outbreaks, all water points functioned properly.
which cannot be reached. From this deeper compartment,
biofilms grow back to the outlets, even from different patient
rooms. Therefore, for infection control, mechanical cleaning
and disinfection of the outlets of the system is often the
maximum achievable goal.

Month May Jun Jul Aug Sep Okt Nov

Week 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

PaƟent isolates A A NT NT A A D E C
A A C A
AA

Environmental Tested 50 50 18 11 55 57 40 40
isolates PosiƟve 996 7 12 4 8 5
Genotyping- results A NT NT NT C A A F
A NT NT NT NT E A G
NR NT NT NT NT E A H
NT NT NT NT NT NT A I
NT NT NT NT NT A J
NT NT NT NT NT C
NT NT NT NT E
NT NT NT
NT NT NT
NT
NT
NT
NT

% positive 18,0 18,0 33,3 63,6 21,8 7,0 20,0 12,5

Interventions 12 34 56 7

Figure 1. Epidemic curve ESBL-positive E.cloacae outbreak. Chronologic schematic overview of the epidemic. Patient isolates. Colour
or rectangle: red; blood culture, yellow; urine, grey: rectal swab. Colour of character: black; haematology patient, red; oncology
patient. Environmental isolates: 321 samples from various water points were tested; 58 (18%) were positive for ESBL-positive E.cloacae
with the epidemic phenotype. Genotyping results (patient and environmental isolates): Genotyping results were obtained by AFLP and/
or wgMLST. A, CeE: genotype of ESBL-positive Enterobacter cloacae strain; italicized ¼ genotyped by wgMLST. NT ¼ not typed. NR ¼ not
related. Interventions: (1) contact-isolation in separate room for positive patients and all contact patients, (2) start of point prevalence
screening of all patients on ward by rectal swab, (3) disinfection of sinks and showers with Na2CO3 on a weekly basis, (4) replacement of
all syphons of sinks on the ward (replacement of shower drains not possible), (5) disinfection of shower drains with chlorine and Na2CO3 on
a daily basis plus closure of culture positive shower drains in the corridor, (6) reopening of showers corridor, (7) termination of weekly
point prevalence screening.

W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209 3

Sampling of patients and environment 6 cm. Toilets were sampled by swabbing under the edge. Fur-
thermore, faucets and refrigerators inpatient rooms were
Environmental samples swabbed.
During the two outbreak periods environmental sampling
was performed on the ward, using Copan Transswab (108C Patient samples
USE)Ò. The interior of sink drains and shower drains were Haematology patients were routinely screened twice a
sampled by inserting the swab and rotating at a depth of about week for colonisation of throat and faeces with Gram-negative

4p 2p 2p 4p
4p
P.24.2 P.24.1
P.29.2

P.20.1 4p

P.21.12 p P.19.1
P.20.1
P.24.1 P.22.1

P.24.2 2 pP.19.1
P.22.1
P.28.1

1p Showerdrain Showerdrain 2p
P.23.1
Showerdrain P.29.2

1p Toilet an
showerdrain
P.18.1
1p
1p
P.19.2
P.20.1 P.24.2
P.28.1
2 pP.18.1
P.19.1
P.19.2

1p 1 pP.24.1
P.24.2
P.23.1 P.29.2

1p 2p

P.24.2

sink

1p
P.20.1
P.28.1

Figure 2. Overview environmental sampling E.cloacae. Situation in the haematology department in week 25. In this figure is indicated
where patients and environmental samples tested positive for ESBL-positive E.cloacae. Inner rectangles: 1p/2p/4p ¼ 1, 2, 4 persons
patient room. Orange: environmental samples were positive for other Gram-negative bacteria. Red: environmental sample(s) positive for
ESBL-positive E. cloacae and other Gram-negative bacteria. In the outer rectangles is indicated which patients had been admitted to the
room before environmental sampling. Two shower drains were both positive at the corridor which were used by multiple patients were
all positive for ESBL-positive E. cloacae.

4 W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209

bacteria, as a part of their intensive chemotherapy treatment. and toilets were cleaned with fluid containing calcium carbo-
The oral combination of ciprofloxacin and fluconazole was used nate (CIF, Unilever, Rotterdam, The Netherlands).
prophylactically for SDD, with the aim of preventing systemic
Gram-negative or fungal infection during the neutropenic Experimental study
phase of their treatment. If bacteria resistant to ciprofloxacin
were cultured from patients, oral colistin was added to bac- We investigated whether toilets might have been a driving
terial SDD. force behind transmission on the ward. During flushing, drop-
lets have the opportunity to spread to the environment,
During the E. cloacae outbreak, present oncology patients because the patient toilets in our hospital do not have a cover
were additionally screened weekly by rectal swab for lid for practical reasons. The experiments were performed in a
E. cloacae carrier status. As no clinical infections occurred toilet room of an unused patient department (all toilets in the
during the P. putida outbreak, oncology patients were not hospital are identical). Experiment 1: 90 mL VisirubÒ fluo-
sampled. rescent concentrate (Hartmann, Nijmegen, The Netherlands)
was mixed with the water present in the flushing cistern
Microbiological methods (estimated volume 9 L). Photographs were taken before and 5
minutes after flushing the toilet, with illumination of the toilet
Phenotypic investigation room using UV-light. Experiment 2: 24,25 mL VisirubÒ con-
Patient screening swabs were cultured overnight on blood centrate was mixed with 24,25 mL demineralized water and
agar and CLED agar at 35 C. As soon as outbreaks were iden- 1.5mL gel-former containing polyacrylamide, C13-14 iso-
tified, environmental samples and rectal swabs from oncology paraffin and laureth-7 (Jojoli, Barendrecht, The Netherlands).
patients were eluted in Trypton Soya Broth (TSB) and cultured The resulting fluorescent mixture was applied underneath the
overnight at 35 C. The next day, the TSB was plated and cul- toilet edge. Again, photographs were taken in a similar
tured overnight on selective CHROMIDÒ ESBL agar (bioMe´rieux, manner.
Marcy-l’E´toile, France) at 35 C. Bacterial strains were identi-
fied and investigated for antibiotic resistance using Vitek-2 Results
(bioMe´rieux, Marcy-l’Etoile, France). ESBL-production from
E. cloacae strains was confirmed by the double disk method ESBL-positive E. cloacae
with cefotaxime, ceftazidime and cefepime with and without
clavulanic acid. Description of the outbreak [Figure 1]
In May 2019, a cluster of three patients with multi-resistant
Genotyping of bacterial strains ESBL-positive E. cloacae was detected on the haematology-
Amplified Fragment Length Polymorphism (AFLP). Cultured oncology department of our hospital. The strains were resist-
isolates were typed by AFLP analysis as described elsewhere ant to the empiric antibiotic regimen on the ward (piperacillin-
[10]. In brief, isolates were resuspended in 10 mM Tris-EDTA tazobactam) and had an identical antibiogram (ESBLþ, cipro-
buffer pH 8.0. Restriction was performed with MseI and EcoRI floxacin R, trimethoprim-sulfamethoxazole R). One neu-
restriction enzymes (New England Biolabs, Massachusetts, tropenic patient had a positive blood culture with this strain,
USA), adaptors were ligated and fragments were amplified by but recovered after switching the antibiotic regime to mer-
PCR with primers specific for the ligated adapters. Following openem. Two of these patients were roommates and all three
restriction and amplification, DNA fragments were separated patients shared the same shower on the ward.
on an ABI Prism 3500XL Genetic Analyser (Applied Biosystems, Six new cases occurred in the subsequent five weeks,
Warrington, UK), after which data were analysed using the despite ongoing enforcement of hand hygiene and contact
Pearson correlation coefficient and were clustered by isolation/cohorting of positive patients in a separate room.
unweighted pair-group matrix analysis (UPGMA) using BioNu- By the end of June, disinfection of sinks and shower drains
merics software v. 7.6 (Applied Maths, St-Martens-Latem, was intensified by replacing all daily and weekly cleaning
Belgium). Isolates clustering above the threshold were products with chlorine at 250 ppm. Patients were instructed
assigned the same AFLP type number. not to leave their personal belongings on the rim of the sink
Whole Genome Multi Locus Sequence Typing (wgMLST). The bowl, to prevent transmission from splashing water from the
first cluster of ESL E.cloacae isolates was also typed by whole drain. In addition, all siphons of sinks on the ward were
genome sequencing (WGS). This was performed as described renewed. As environmental samples remained positive for
elsewhere [11]. Isolates clustering within an allelic difference E. cloacae, a weekly treatment with biofilm degrading liquid
of 20 or less were assigned to the same cluster. Sequencing caustic soda (Senzora BV, Deventer, The Netherlands) for five
data were deposited at European Nucleotide Archive (ENA) minutes was added for every sink drain and toilet. After this
under BioProject PRJEB46126. intervention the incidence of newly colonized patients
declined gradually over time.
Environmental cleaning and disinfection on the ward In the peak of the outbreak, a change in the antibiotic
regimen of SDD for neutropenic haematology patients, from
The sanitary facilities of the ward were cleaned daily with ciprofloxacin to colistin, was considered an optional alter-
moist microfiber cloth and toilets with sanitary cleaner con- native intervention. The epidemic strain was resistant to
taining alkylalcoholethoxylate, aliphatic alcohol and 4-terr- ciprofloxacin, and more than half of the patients on the ward
butylcyclohexylacetate (Taski Sani 100, Diversey, Utrecht, The were treated with SDD, so this might have contributed to the
Netherlands). Floor drains of showers were disinfected with rapid dissemination. Eventually, with the decline of new
chlorine on a weekly basis for a duration of at least 5 minutes, patient cases, this intervention was not effectuated.

W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209 5

Figure 3. Whole Genome Sequencing results ESBL-E.cloacae. Minimum spanning tree of wgMLST of ESBL-positive E. cloacae. Each circle
represents one or multiple isolates, depending on the circle size and lines between circles indicate the allelic distance between the
indicated isolates. Isolates are coloured by origin: patient isolates (green), environmental isolates (red) and reference non-related
isolates (blue). Isolates from patients and the environment that cluster together within the cut-off value are depicted with a grey
line zone and indicated as cluster A.

A final round of environmental specimens (taken at the Multi-drug-resistant Pseudomonas putida
end of August) revealed eight positive environmental cul-
tures from which five isolates belonged to genotype A. In Description of the outbreak [Figure 4]
retrospect, this could be explained by the suboptimal In August 2020, a cluster of four patients with MDR P. putida
adherence to the intensified instructions for disinfection by was noticed in surveillance rectal cultures of haematology
the cleaning personnel. From week 35 on, genotype A patients. The strains were resistant to the empiric antibiotic
E. cloacae was not identified in weekly screenings of regimen on the ward (piperacillin-tazobactam) and had an
patients, and environmental samples in November revealed identical antibiogram (ceftazidime I or R, meropenem R, ami-
only other genotypes. noglycosides R, ciprofloxacin R, colistin S).
New cases (n¼5) occurred in the subsequent two months,
Environmental samples and patient samples [Figure 2] despite enforcement of hand hygiene and contact isolation/
In June and July 2019, 47/241 (19.5%) of environmental cohorting in a separate room of positive patients.
specimens cultured E. cloacae with an identical antibiogram as In contrast to the E. cloacae outbreak, no clinical cultures
the initial epidemic strain, among which three were typed as became positive with MDR P. putida, and the incriminated
genotype A (three belonged to other genotypes and 41 were strains disappeared from rectal cultures of individual positive
not typed). Positive patients were identified in the majority of patients as soon as SDD was changed from ciprofloxacin to
patient rooms. colistin. The incidence of colonization reduced spontaneously,
so therefore interventions were not necessary. Suspected
Genotyping [Figure 3] environmental sources, such as the shower and sink of a patient
All patient strains during the initial outbreak period in May room that was shared by several positive patients, and the ice
(n¼ 4) appeared to be identical by AFLP and wgMLST (AFLP- cube machine of the ward, were cultured but were negative.
type A). Additional isolates were therefore typed by AFLP only. In October, four new patients became positive with a phe-
In subsequent AFLP-analysis there appeared to be the simul- notypically identical P. putida. Therefore, the 30 toilet edges
taneous presence of multiple genotypes on the ward. In the in all rooms where positive patients had been admitted, were
period MayeJune, six of seven strains were identical (genotype cultured for P. putida. Only one toilet edge was positive with a
A). In the period JulyeAugust three out of six strains were different genotype. It turned out that the four patient strains
genotype A. were different from each other and only one was colonized
Typing of 18 environmental isolates demonstrated 3/6 with the outbreak strain (genotype 3). Since then, no new
genotype A in the period MayeJuly, 7/8 genotype A in August patients carrying P. putida have been identified. Unexpectedly,
and 0/4 genotype A in November. in the last week of November four out of five genotyped

6 W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209

Figure 4. Epidemic curve multi-resistant Pseudomonas putida outbreak. Chronologic schematic overview of the epidemic. Patient
isolates. Only positive cultures from rectal swabs for Selective Digestive Decontamination were involved. Environmental cultures: week
38; shower and sink in patient room frequently occupied by positive patients, week 40; ice cube machine; week 41; various water tap
points (water from toilets, siphons of basins, buckets used by cleaning personnel), week 48; ridges of 7 toilets from patient rooms of
positive patients (note: these cultures were negative for ESBLþ E.cloacae). Genotyping results (patient and environmental isolates):
3e7: genotype of multi-resistant Pseudomonas putida strain. NT ¼ not typed. Interventions: no interventions were carried out.

environmental strains from toilets were identified as the epi- transmission. This hypothesis was supported by experimental
demic P. putida (genotype 3). results, which proved that by flushing toilets with a fluorescent
dye, droplets were clearly disseminated to the environment in
Environmental samples [Figure 4] toilet rooms. For E. cloacae, various interventions resulted in
In SeptembereNovember 2020, 7/44 (16%) of environmental the discontinuation of transmission among patients. For
cultures were positive for P. putida with an antibiogram iden- P. putida, transmission disappeared without other inter-
tical to the strain found in the cluster in August. From these ventions beside changing SDD from ciprofloxacin to colistin in
isolates four belonged to the epidemic genotype 3, two to individual colonized haematology patients.
other genotypes and one was not typed.
While the E. cloacae transmission was first discovered in
Genotyping clinical cultures of blood and urine, P. putida was only found in
Three out of four strains of the initial cluster were deter- rectal surveillance cultures. P. putida rectal culture positivity
mined to be identical by AFLP (genotype 3). During the out- was mainly noticed immediately after admission to the ward
break different AFLP variants were found, from which some and disappeared as soon SDD was changed. For both outbreaks,
were shared between patients and some between patients and environmental cultures of wet points remained positive for
environment. Of the new cases in SeptembereOctober, 2/5 more than a month after the last positive patient was identi-
typed isolates belonged to genotype 3 and of the seven positive fied. The latter finding implicates that after disinfection of sink
environmental samples, four were genotype 3. or shower drains, biofilm is still present in the deeper com-
partment of the hospital drainage system. Moreover, reconta-
Experimental study [Figure 5] mination of the water from a biofilm underneath the toilet rim
during flushing is a possibility (Figure 5). Bacteria in this biofilm
Experiment 1: fluorescent remnants of flushing water were remain an ongoing threat for colonization of patients during
seen throughout the toilet bowl and some droplets outside their stay in the hospital. As the drainage systems can often not
were identified (Figure 5A). Experiment 2: flushing water was be replaced, the most efficient solution is to “keep the monster
able to remove some fluorescent gel underneath the toilet inside” by removing the biofilm at the outlets at regular
edge, which could in theory be further transmitted to the intervals combined with disinfection of these sites. The most
environment by successive flushes (Figure 5B). efficient and achievable method is still under debate. Recent
technical solutions, such as UV disinfection and ozonisation of
Discussion water seem promising [12]. Innovative design of sinks can
reduce the contamination of the near surroundings with bac-
In this study we describe the simultaneous colonization of teria originating from the biofilm [13]. The introduction of self-
patients and water related devices with ESBL-positive disinfecting siphons gave excellent results [14,15]. Fur-
E. cloacae or MDR P. putida on the haematology-oncology thermore, a critical appraisal of the necessity of all water
ward of our hospital. A mix of genotypes were isolated in points in the hospital is indispensable; unnecessary ones should
both cases, but a dominant genotype of either E. cloacae or be removed and the remaining points should be strictly divided
P. putida was shared by both patients and environment, sug- into incoming and outgoing points to prevent cross-
gesting that environmental sources played a role in contamination [16]. For transmission prevention of highly
resistant opportunistic plumbing premise pathogens, design

W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209 7

Figure 5. Experimental study flushing toilet. Experiments were performed in a toilet room of a unused patient department. Experiment
1: 90 mL VisirubÒ concentrate (Hartmann, Nijmegen, The Netherlands) was mixed with the water present in the flushing cistern (esti-
mated volume 9 L). Photographs were taken before and 5 minutes after flushing the toilet, with illumination of the toilet room using UV-
light. UV-positive remainders of droplets were identified inside as well as outside the toilet bowl. Experiment 2: 24,25 mL VisirubÒ
concentrate was mixed with 24,25 demineralized water and 1,5 mL gel-former (Jojoli, Barendrecht, The Netherlands). The resulting
fluorescent mixture was applied underneath the toilet edge. Again, photographs were taken in a similar manner. Flushing water was able
to remove the gel from the toilet.

8 W.C. van der Zwet et al. / Infection Prevention in Practice 4 (2022) 100209

and construction of the water system of newly built hospitals is Conclusions
critical [17]. Also the implementation of waterless patient care
is an expensive, but effective method to discontinue hospital In conclusion, the patient environment is increasingly con-
transmission [18]. sidered as a major source of transmission of nosocomial bac-
teria [26]. The drainage system of the hospital is an important
For situations wherein the former solutions are not feasible, reservoir of multi-resistant bacteria, threatening admitted
the most effective intervention for disinfection and removal of patients. In existing hospitals, biofilms in the drainage systems
biofilm is still under debate. Recently, Ledwoch et al. pub- can often not be removed. Therefore, it is important that in
lished a novel in vitro biofilm model to investigate this topic. In (re)building plans for hospitals a plan for prevention of noso-
a study comparing four methods for disinfection, peracetic comial transmission from environment to patients is incorpo-
acid 4000 ppm was superior to alternatives, resulting in a >4 rated. For existing, maybe older, hospital buildings, a water
log reduction in viability in all drain sections [19]. Another safety plan for haematology-oncology departments should be
weak point in manual disinfection is the correct implementa- instituted [27]. Furthermore, where technical solutions are not
tion by the environmental services workers. In the E. cloacae available, regular training of cleaning personnel is of utmost
outbreak, we discovered that the intensified disinfection importance.
strategy was not strictly followed by all members of the team,
which contributed to the delayed termination of the outbreak. Credit statement of authorship
In this context, not only the type of disinfectant but also the
contact time with the various parts of the drains is crucial. WC Van der Zwet: Conceptualization, methodology, formal
Education and feedback by regular audit are essential for high analysis, writing original draft, writing review and editing. IEJ
standard cleaning and disinfection in the hospital [20]. Fur- Nijsen: Methodology, formal analysis, visualization, data
thermore, we concluded that biofilms do not only occur in the curation, writing review and editing. C Jamin: Investigation,
drainage system but also underneath the rim of the toilet seats. visualization, writing review and editing. LB Van Alphen:
Technical solutions, such as rimless toilets, are helpful in pre- Investigation, visualization, writing review and editing. CJH
vention of biofilms that are difficult to remove. Von Wintersdorff: Investigation, visualization, writing review
and editing. AMP Demandt: Writing review and editing. PHM
High antibiotic use is a well-known risk factor for the Savelkoul: Writing review and editing, supervision.
selection of resistant bacteria. The majority of patients on the
ward were haematology patients receiving SDD, as part of their Conflict of interest statement
treatment, for prevention of bacteraemia and mortality. In
case of resistance in Gram-negative rods, ciprofloxacin is The authors have no conflicts of interest to declare.
changed to a combination of trimethoprim-sulfamethoxazole
and colistin. As a substantial part of the patient population Funding
was treated with an antibiotic for which the E. cloacae strains
were resistant, this was considered as a possible driving force No funding was received for this work.
behind the ongoing transmission on the ward, because the
colonization resistance in these patients was lowered. Ethics and patient consent
Switching to another antibiotic class could be an effective
intervention. Frakking et al. used the discontinuation of Informed consent was not gained from patients involved in
ciprofloxacin prophylaxis in haematology patients in a bundle this outbreak. All patients were treated according to clinical
of interventions which ended a large and persistent outbreak judgement and infection control practices in order to treat
caused by vancomycin-resistant Enterococcus faecium, which them and control the outbreak according to local guidelines.
is less pathogenic than Enterobacter spp [21]. Verlinden et al. Patients did not undergo randomisation or intervention for the
found no significant increase in serious infectious complica- purpose of this report. Data has been analysed and presented
tions with the discontinuation of prophylaxis and a decrease in anonymously.
fluoroquinolone resistant and ESBL-producing Gram-negative
bacteria [22]. Furthermore, the effectivity of ciprofloxacin References
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Sewage system as a source of Germs and

Sink traps as the source of transmission of OXA-48– Abstract
producing Serratia marcescens in an intensive care Background: Carb
unit attributed to patie
successful containm
Gili Regev-Yochay MD, MS, Gill Smollan MD , Ilana Tal RN , Nani Pinas Zade recognizing the sin
RN , Yael Haviv MD , Valery Nudelman RN , Ohad Gal-Mor PhD, Hanaa Jaber Methods: The She
BsC , Eyal Zimlichman MD6 , Nati Keller MD and Galia Rahav MD, closed rooms. Activ
case was defined a
Infection Control & Hospital Epidemiology (2018), 39, cause analysis was
1307–1315 doi:10.1017/ice.2018.235 agar CRE, and carb
R. Environmental a
Results: From Janu
these were S. marc
factor in all cases w
detected in 2 sink o
measures, measure
and (2) ,efforts, w
educational interve
contamination pre
Conclusions: Despi
year, the outbreak
reservoirs played a

‫בס"ד‬

bacterial outbreak-new studies

bapenemase-producing Enterobacteriaceae (CPE) outbreaks are mostly
ent-to-patient transmission via healthcare workers. Objective: We describe
ment of a prolonged OXA-48–producing S. marcescens outbreak after
nk traps as the source of transmission.
eba Medical Center intensive care unit (ICU), contains 16 single-bed, semi-
ve CPE surveillance includes twice-weekly rectal screening of all patients. A
as a patient detected with OXA-48 CPE >72 hours after admission. A root-
s used to investigate the outbreak. All samples were inoculated on chrom-
bapenemase genes were detected using commercial molecular Xpert-Carba-
and patient S. marcescens isolates were characterized using PFGE.
uary 2016 to May 2017, 32 OXA-48 CPE cases were detected, and 81% of
cescens. A single clone was the cause of all but the first 2 cases. The common
was the use of relatively large amounts of tap water. The outbreak clone was
outlets and 16 sink traps. In addition to routine strict infection control
es taken to contain the outbreak included (1) various sink decontamination
hich eliminated the bacteria from the sink drains only temporarily
ention that engaged the ICU team and lead to high adherence to ‘sink-
evention guidelines.’ No additional cases were detected for 12 months.
ite persistence of the outbreak clones in the environmental reservoir for 1
k was rapidly and successfully contained. Addressing sink traps as hidden
a major role in the intervention.

Spread from the Sink to the Patient: In Situ Study ABSTRACT There
Using Green Fluorescent Protein (GFP)-Expressing as often carrying
Escherichia coli To Model Bacterial Dispersion from traps to vulnerabl
Hand-Washing Sink-Trap Reservoirs the wastewater o
report the use of
Shireen Kotay, a Weidong Chai,a William Guilford,b Katie Barry, a Amy J. green fluorescent
Mathersa,c surrounding envir
from the P-trap to
Applied and Environmental Microbiology from a faucet. Ho
April 2017 Volume 83 Issue 8 e03327-16 , a GFP-t in the P-
expressing E. coli-
Sink-Related Outbreaks and Mitigation Strategies in strainer. This subs
Healthcare Facilities in.) during faucet
by retrograde tran
Leighanne O. Parkes1 & Susy S. Hota2, in droplet dispers
dispersion directl
Current Infectious Disease Reports (2018) 20:42 transmission of ba
https://doi.org/10.1007/s11908-018-0648-3
Abstract Purpose o
hospital sinks and e
The effectiveness o
investigational stra
Outbreaks of hospi
They can be attribu
the formation and
behaviors. Risk mit
sink colonization m
more investigation.

have been an increasing number of reports implicating
g genes of drug resistance from colonized sink Gammaproteobacteria
le hospitalized patients. However, the mechanism of transmission from
of the sink P-trap to patients remains poorly understood. Herein we

a designated hand-washing sink lab gallery to model dispersion of
t protein (GFP)-expressing Escherichia coli from sink wastewater to the
ronment. We found no dispersion of GFP-expressing E. coli directly
o the sink basin or surrounding countertop with coincident water flow
owever, when the GFP-expressing E. coli cells were allowed to mature
-trap under conditions similar to those in a hospital environment
-containing putative biofilm extended upward over 7 days to reach the
sequently resulted in droplet dispersion to the surrounding areas (30
operation. We also demonstrated that P-trap colonization could occur
nsmission along a common pipe. We postulate that the organisms
sion rather than resultingmobilize up to the strainer from the P-trap,
ly from the P-trap. This work helps to further define the mode of
acteria from a P-trap reservoir to a vulnerable hospitalized patient.

of Review In this review, we summarize recent outbreaks attributed to
examine design features and behaviors that contributed to these outbreaks.
of various risk mitigation strategies is presented. Finally, we examine
ategies targeted at reducing the risk of sink-related infections. Recent Findings
ital sink-related infections involve a diverse spectrum of microorganisms.
uted to defects in sink design and hospital wastewater systems that promote
dispersion of biofilm, as well as healthcare practitioner and patient
tigation strategies are often bundled; while they may reduce clinical cases,
may persist. Novel approaches targeting biofilms show promise but require
. Summary Emphasis should be placed on optimizing best practices in sink

Control of Multidrug-Resistant Pseudomonas design and placeme
aeruginosa in Allogeneic Hematopoietic Stem Cell surveillance and pr
Transplant Recipients by a Novel Bundle Including Background. Infec
Remodeling of Sanitary and Water Supply Systems an important caus
hematopoietic ste
Annelene Kossow, 1 Stefanie Kampmeier, 1 Stefanie Willems,1 Wolfgang E. reservoir and sou
Berdel,2 Andreas H. Groll,3 Birgit Burckhardt,3 Claudia Rossig,3 Christoph from these reserv
Groth,2 Evgeny A. Idelevich,4 Frank Kipp,1 Alexander Mellmann,1,a and installations as th
Matthias Stelljes2, Methods. During
2014) we implem
The Author 2017. Published by Oxford University contamination by
Press for the Infectious Diseases Society of America. shower drain, disi
All rights reserved. For permissions, e-mail: year study period
[email protected]. DOI: (colonized and/or
10.1093/cid/cix465 environmental oc
sequencing of nos
isolates.
Results. Whereas
and 2013, the num
MDRPA similarly d
decreased in toile
8.1% to 3.0%, resp
relationships betw
Conclusions. Hosp
contamination by
lethal MDRPA infe

ent to prevent infections. Hospitals should consider developing a rational
revention strategy based on the current design and state of their sinks.
ctions by multidrug-resistant Pseudomonas aeruginosa (MDRPA) are
se of morbidity and mortality in patients after allogeneic
em cell transplantation (HSCT). Humid environments can serve as a
urce of infection by this pathogen. To minimize the risk of infection
voirs, we performed extensive remodeling of sanitation and water
he focus of our hygiene bundle.
the reconstruction of our transplantation unit (April 2011–April
mented several technical modifications to reduce environmental
y and subsequent spreading of MDRPA, including a newly designed
infecting siphons underneath the sinks, and rimless toilets. During a 3-
d (2012–2014), we tracked the number of patients affected by MDRPA
r infected) and the outcome of infected patients and monitored the
ccurrence of this pathogen. We further performed whole-genome
socomial MDRPA strains to evaluate genotypic relationships between

s 31 (9.2%; 18 colonized, 13 infected) patients were affected in 2012
mber decreased to 3 in 2014 (17%; 3 colonized, 0 infected). Lethality by
decreased from 3.6% to 0%. Environmental detection of MDRPA
ets from 18.9% in 2012–2013 to 6.1% in the following year and from
pectively, in shower outlets. Whole-genome sequencing showed close
ween environmental and patient-derived isolates.
pital construction measures aimed at controlling environmental
y and spread of MDRPA are effective at minimizing the risk of highly
ections.

Prevalence of E. coli, Salmonella, and Listeria spp. as Since knowledge
potential pathogens: A comparative study for biofilm of illuminated, a fe
sink drain environment various househo
aims to (a) asses
Mohamed Azab El-Liethy | Bahaa A. Hemdan | Gamila E. El-Tawee natural biofilm t
and Listeria spp.
wileyonlinelibrary.com/journal/jfs bathroom (n = 1
© 2020 Wiley Periodicals LLC. 1 of 10 bacterial species
https://doi.org/10.1111/jfs.12816 verification of is
J Food Saf. 2020 ;e12816 estimated numb
were obtained f
hospital, respect
counts at low te
Meanwhile, E. co
to the other two
Salmonella, and
then the hospita
.0001) with sign
potential of hou
noticeable. Such
threat to human

e and understanding of waterborne pathogens and their diseases are well
ew research publications on the prevalence of pathogenic microorganisms in
old sink drain pipes are often not extensively examined. Therefore, this study
ss and monitor the densities of the bacterial community in the different
that grow on plastic pipelines, and (b) to detect Escherichia coli, Salmonella,
. from natural biofilm samples that are collected from the kitchen (n = 30),
10), laboratories (n = 13), and hospital (n = 8) sink drainage pipes. Three
s selected were assessed using a culture-dependent approach followed by
solates using both BIOLOG GEN III and polymerase chain reaction. The
ber of each bacterium was 122 isolates, while 60, 20, 26, and 16 isolates
from the natural biofilm samples, kitchen, bathroom, laboratories, and
tively. As for the tests, in all types of biofilm samples, the overall bacterial
emperature (22C) were higher than those at high temperature (37C).
oli had the most significant number of bacterial microorganisms compared
o pathogens. Additionally, the most massive cell densities of E. coli,
d Listeria species were discovered in the biofilm collected from the kitchen,
al. Statistically, the results reveal that there is a positive correlation (p ≥
nificance between the sources of biofilm. This work certainly makes the
usehold sink drain pipes for reservoir contagious pathogens more explicitly
h knowledge would also be beneficial for prospective consideration of the
n public health and the environment

Investigation using whole genome sequencing of a ABSTRACT Following notif
prolonged restaurant outbreak of Salmonella identified 82 cases linked
Typhimurium linked to the building drainage system, Seventy-two cases had an
England, February 2015 to March 2016 nucleotide polymorphism
restaurant and subsequen
John Mair-Jenkins1,2,3, Roberta Borges-Stewart, Caroline Harbour, Judith (adjusted odds ratios (AO
Cox-Rogers , Tim Dallman, Philip Ashton, Robert Johnston, Deborah Modha , food/ water testing, and a
Philip Monk⁴, Richard Puleston undertaken, including hyd
investigation, environmen
Article published online: 31 May 2013 Clin Microbiol matching the outbreak pro
Infect 2013; 19: E490–E498 10.1111/1469-0691.12288 reservoir of bacteria in dra
Ineffective drain water-tra
Contaminated Handwashing Sinks as the Source of a aerosols into the kitchen e
Clonal Outbreak of KPC-2-Producing Klebsiella oxytoca inspection of drainage sys
on a Hematology Ward. ABSTRACT We investigate
(KPC)-producing Klebsiella
Eva Leitner, a Gernot Zarela Josefa Luxner,a Kathrin Herzog,b Shiva Pekard- in sink drains in 4 patient r
Amenitsch,c Martin Hoenigl,d Thomas Valentin,d Gebhard Feierl,a Andrea J. relatedness of patient and
Grisold,a Christoph Högenauer,b Heinz Sil l,e Robert Krause ,d Ines Zollner- blaTEM-1 genes and were
Schwetz producing K. oxytoca, and

Antimicrobial Agents and Chemotherapy January 2015
Volume 59 Number 1

fication of a Salmonella enterica serovar Typhimurium gastroenteritis outbreak, we
to a restaurant with symptom onset from 12 February 2015 to 8 March 2016.
n isolate matching the nationally unique whole-genome sequencing profile (single
(SNP) address: 1.1.1.124.395.395). Interviews established exposure to the
nt case-control analysis identified an association with eating carvery buffet food
OR): 20.9; 95% confidence interval (CI): 2.2 – ∞). Environmental inspections,
a food trace-back investigation were inconclusive. Repeated cycles of cleaning were
drogen peroxide fogging, however, transmission continued. After 7 months of
ntal swabbing identified 106 isolates from kitchen surfaces and restaurant drains
ofile. We found structural faults with the drainage system and hypothesized that a
ain biofilm and underfloor flooded areas may have sustained this outbreak.
aps (U-bends) may have also contributed by allowing transmission of contaminated
environment. These findings suggest that routine swabbing of sink drain points and
stems should be considered in future outbreak scenarios.
ed sinks as possible sources of a prolonged Klebsiella pneumonia carbapenemase
a oxytoca outbreak. Seven carbapenem-resistant K. oxytoca isolates were identified
rooms and in the medication room. Investigations for resistance genes and genetic
d environmental isolates revealed that all the isolates harbored the blaKPC-2 and
e genetically indistinguishable. We describe here a clonal outbreak caused by KPC-2-
d handwashing sinks were a possible reservoir.

Role of the environment in transmission of Gram negative bacteria in two ABS
consecutive outbreaks in a hematology-oncology department con
exte
W.C. van der Zwet a, *, I.E.J. Nijsen a , C. Jamin a , L.B. van Alphen a , C.J.H. von Wintersdorff a , A.M.P. yea
Demandt b , P.H.M. Savelkoul hou
com
2022 The Authors. Published by Elsevier Ltd on behalf of The Healthcare and
Infection Society. This is an open access article under the CC BY license com
(http://creativecommons.org/licenses/by/4.0/). gen
blaK
exte
vast
spe
pop
high
the
isola
reas
nos
was
und
infe

In C

tran
imp
hos
imp
tran
hos
inst
clea

STRACT The hospital environment is a potential reservoir of bacteria with plasmids
nferring carbapenem resistance. Our Hospital Epidemiology Service routinely performs
ensive sampling of high-touch surfaces, sinks, and other locations in the hospital. Over 2
ars, additional sampling was conducted at a broader range of locations, including
usekeeping closets, wastewater from hospital internal pipes, and external manholes. We
mpared these data with previously collected information from 5 years of patient clinical
d surveillance isolates. Whole-genome sequencing and analysis of 108 isolates provided
mprehensive characterization of blaKPC/blaNDM-positive isolates, enabling an in-depth
netic comparison. Strikingly, despite a very low prevalence of patient infections with
KPC-positive organisms, all samples from the intensive care unit pipe wastewater and
ernal manholes contained carbapenemase-producing organisms (CPOs), suggesting a
t, resilient reservoir. We observed a diverse set of species and plasmids, and we noted
ecies and susceptibility profile differences between environmental and patient
pulations of CPOs. However, there were plasmid backbones common to both populations,
hlighting a potential environmental reservoir of mobile elements that may contribute to

spread of resistance genes. Clear associations between patient and environmental
ates were uncommon based on sequence analysis and epidemiology, suggesting
sonable infection control compliance at our institution. Nonetheless, a probable
socomial transmission of Leclercia sp. from the housekeeping environment to a patient
s detected by this extensive surveillance. These data and analyses further our
derstanding of CPOs in the hospital environment and are broadly relevant to the design of
ection control strategies in many infrastructure settings.

Conclusion, the patient environment is increasingly considered as a major source of

nsmission of nosocomial bacteria [26]. The drainage system of the hospital is an
portant reservoir of multi-resistant bacteria, threatening admitted patients. In existing
spitals, biofilms in the drainage systems can often not be removed. Therefore, it is
portant that in (re)building plans for hospitals a plan for prevention of nosocomial
nsmission from environment to patients is incorporated. For existing, maybe older,
spital buildings, a water safety plan for hematology-oncology departments should be
tituted. Furthermore, where technical solutions are not available, regular training of
aning personnel is of utmost importance

Investigation of a Cluster of Sphingomonas koreensis Infections BAC
opp
Ryan C. Johnson, Ph.D., Clay Deming, M.S., Sean Conlan, Ph.D., Caroline J. Zellmer, B.S., Angela V. clus
Michelin, M.P.H., ShihQueen Lee-Lin, M.S., Pamela J. Thomas, Ph.D., Morgan Park, Ph.D., Rebecca A. ME
Weingarten, Ph.D., John Less, P.E., C.H.F.M., John P. Dekker, M.D., Ph.D., Karen M. Frank, M.D., Ph.D., mu
Kimberlee A. Musser, Ph.D., John R. McQuiston, Ph.D., David K. Henderson, M.D., Anna F. Lau, Ph.D., Tara the
N. Palmore, M.D., and Julia A. Segre, Ph.D the
me
The New England Journal of Medicine 379;26 nejm.org December 27, 2018 hos
isol
RE
the
mo
Ret
Clin
dec
elu
isol
rem
sca
CO
kor
Cen
infe

CKGROUND Plumbing systems are an infrequent but known reservoir for
portunistic microbial pathogens that can infect hospitalized patients. In 2016, a
ster of clinical sphingomonas infections prompted an investigation.
ETHODS We performed whole-genome DNA sequencing on clinical isolates of
ultidrug-resistant Sphingomonas koreensis identified from 2006 through 2016 at
e National Institutes of Health (NIH) Clinical Center. We cultured S. koreensis from
e sinks in patient rooms and performed both whole-genome and shotgun
etagenomic sequencing to identify a reservoir within the infrastructure of the
spital. These isolates were compared with clinical and environmental S. koreensis
lates obtained from other institutions.
ESULTS The investigation showed that two isolates of S. koreensis obtained from
e six patients identified in the 2016 cluster were unrelated, but four isolates shared
ore than 99.92% genetic similarity and were resistant to multiple antibiotic agents.
trospective analysis of banked clinical isolates of sphingomonas from the NIH
nical Center revealed the intermittent recovery of a clonal strain over the past
cade. Unique single-nucleotide variants identified in strains of S. koreensis
ucidated the existence of a reservoir in the hospital plumbing. Clinical S. koreensis
lates from other facilities were genetically distinct from the NIH isolates. Hospital
mediation strategies were guided by results of microbiologic culturing and fine-
ale genomic analyses.
ONCLUSIONS This genomic and epidemiologic investigation suggests that S.
reensis is an opportunistic human pathogen that both persisted in the NIH Clinical
nter infrastructure across time and space and caused healthcare-associated
ections. (Funded by the NIH Intramural Research Programs.)

Droplet- Rather than Aerosol-Mediated ABSTRACT An alarming ris
Dispersion Is the Primary Mechanism of widespread acknowledgm
Bacterial Transmission from Contaminated patient care areas. An ear
Hand-Washing Sink Traps (GFP-E. coli) as a model o
The present study further
Shireen M. Kotay, a Rodney M. Conlan,b Christine Ganim,C Katie Replicate hand-washing s
Barry, a Bryan E. Christensen,B Amy J. Mathersa, qualitative (settle plates)
was captured with settle
January 2019 Volume 85 Issue 2 e01997-18 In contrast, no dispersal w
Applied and Environmental Microbiology theory that bacteria aero
diminished substantially w
associated with larger dro

Spread from the Sink to the Patient: In Situ Study Using ABSTRACT There have been an inc
Green Fluorescent Protein (GFP)-Expressing Escherichia genes of drug resistance from colo
coli To Model Bacterial Dispersion from Hand-Washing transmission from the wastewater
Sink-Trap Reservoirs of a designated hand-washing sink
Escherichia coli from sink wastewa
Shireen Kotay,a Weidong Chai,a William Guilford,W Katie coli directly from the P-trap to the
Barry, a Amy J. Mathers However, when the GFP- expressi
those in a hospital environment, a
April 2017 Volume 83 Issue 8 e03327-16 Applied and reach the strainer. This subsequen
Environmental Microbiology operation. We also demonstrated
pipe. We postulate that the organ
rather than dispersion directly fro
from a P-trap reservoir to a vulner

se in hospital outbreaks implicating hand-washing sinks has led to
ment that sinks are a major reservoir of antibioticresistant pathogens in
rlier study using green fluorescent protein (GFP)-expressing Escherichia coli
organism demonstrated dispersal from drain biofilms in contaminated sinks.
r characterizes the dispersal of microorganisms from contaminated sinks.
sinks were inoculated with GFP-E. coli, and dispersion was measured using

and quantitative (air sampling) methods. Dispersal caused by faucet water
plates and air sampling methods when bacteria were present on the drain.
was captured without or in between faucet events, amending an earlier
osolize from the P-trap and disperse. Numbers of dispersed GFP-E. coli cells
within 30 minutes after faucet usage, suggesting that the organisms were
oplet-sized particles that are not suspended in the air for long periods.

creasing number of reports implicating Gammaproteobacteria as often carrying
onized sink traps to vulnerable hospitalized patients. However, the mechanism of
r of the sink P-trap to patients remains poorly understood. Herein we report the use
k lab gallery to model dispersion of green fluorescent protein (GFP)-expressing
ater to the surrounding environment. We found no dispersion of GFP-expressing E.
e sink basin or surrounding countertop with coincident water flow from a faucet.
ing E. coli cells were allowed to mature in the P-trap under conditions similar to
a GFP-expressing E. coli-containing putative biofilm extended upward over 7 days to
ntly resulted in droplet dispersion to the surrounding areas (30 in.) during faucet
d that P-trap colonization could occur by retrograde transmission along a common
nisms mobilize up to the strainer from the P-trap, resulting in droplet dispersion
om the P-trap. This work helps to further define the mode of transmission of bacteria
rable hospitalized patient.

ENSIVELY DRUG-RESISTANT PSEUDOMONAS SUMMARY. Infections are still the ma
AERUGINOSA OUTBREAK IN A BURN UNIT: outbreaks in critical care and burn un
MANAGEMENT AND SOLUTIONS Pseudomonas aeruginosa in the Burn
descriptive study of all cases, a bacter
Aguilera-Sáez J.,* Andreu-Solà V., Larrosa Escartín N., environmental study were performed
Rodríguez Garrido V., Armadans Gil L., Sánchez García healthcare workers of all infected or c
J.M., Campins M., Baena Caparrós J., Barret J.P for possible sources of infection. The
patients were infected or colonized a
Annals of Burns and Fire Disasters - vol. XXXII - n. 1 - different rooms of the Unit. After app
March 2019 disinfection of the hot water installat
antibacterial filtration devices in all th

The sink as a potential source of transmission Background: Carbapenemase-p
of carbapenemase-producing public health threat. In the Uni
Enterobacteriaceae in the intensive care unit in 2010 to 35 cases in 2015. Be
during their stay in the same ro
Deborah De Geyter , Lieve Blommaert , Nicole Verbraeken1 , was relatively short and the str
Mark Sevenois , Luc Huyghens , Helena Martini , Lieve Covens , resistance, the hypothesis was
Denis Piérard1 and Ingrid Wybo Methods and results: Environm
Besides other strains, Citrobact
De Geyter et al. Antimicrobial Resistance and investigate the phylogenetic re
Infection Control (2017) 6:24 The strains isolated from patien
patient transmission. In total, 7
control the outbreak, the sinks
flushed every morning with a g
discontinuation of the outbrea
Conclusions: This outbreak hig
become a potential source of C

ain cause of mortality in burn patients. Multidrug-resistant bacteria can cause
nits. We describe an outbreak of infection by extensively drug-resistant
n Unit of a University Hospital in Barcelona (Spain) between April and July 2016. A
rial colonization screening of all admitted patients and a microbiological
d in order to detect a possible common focus. Contact isolation and colorization of
colonized patients were applied. Environmental control measures were instituted

outbreak was caused by a strain of P. aeruginosa only sensitive to colistin. Ten
and two of them died. The same strain was detected in several taps and drains in
plying control measures, changing faucets and drains, carrying out thermal
tion of the unit, disinfecting the rooms with ultraviolet radiation, and placing
he taps among other measures, effective control of the outbreak was achieved.

producing Enterobacteriaceae (CPE) are emerging pathogens that represent a major
iversity Hospital of Brussels, the incidence of new patients with CPE rose from 1 case
etween January and August 2015, five patients became infected/colonized with CPE
oom in the intensive care unit (ICU). Since the time period between those patients
rains belonged to different species with different antibiograms and mechanisms of
that the environment could be a possible source of transmission.
mental samples suggested that a contaminated sink was the source of the outbreak.
ter freundii type OXA-48 was frequently isolated from patients and sinks. To
elationship between those strains, pulsed-field gel electrophoresis was performed.
nts and the sink in the implicated room were highly related and pointed to sink-to-
7 of 8 sinks in the isolation rooms of the ICU were found to be CPE contaminated. To
s and their plumbing's were replaced by new ones with another structure, they were
glycoprotein solution and routines regarding sink practices were improved leading to
ak.
ghlights that hospital sink drains can accumulate strains with resistance genes and
CPE.

Sources of sporadic Pseudomonas aeruginosa Backgroun
colonization/infections in surgical ICUs: Association with aeruginosa
contaminated sink trap importanc
colonizatio
ZhaoYan Zhou , BiJie Hu , XiaoDong Gao, Rong Bao , Min Chen , HuaYin Li sporadic P
further ana
2016 Japanese Society of Chemotherapy and The Japanese care units
Association for Infectious Diseases. Published by Elsevier Ltd. Methods:
All rights reserved was perfor
outbreak,
http://dx.doi.org/10.1016/j.jiac.2016.03.016 1341-321X/© Pulsed fiel
samples ha
hospitalize
approxima
exogenous
contamina
exogenous
in SICU-2 (
a higher le
other patie
Conclusio
aeruginosa
identificati
infections

nd: Many studies have reported the hospital outbreaks of Pseudomonas
a due to crosscontamination between patients and water fittings, but the
ce of water fittings as sources of sporadic P. aeruginosa
ons/infections remains ambiguous. Aim: To investigate the sources of
P. aeruginosa colonizations/infections in a clinical intensive surveillance, and
alysis the potential of sink trap for P. aeruginosa transmission in intensive
(ICUs).
Patients monitoring and targeted environmental screening for P. aeruginosa
rmed prospectively over a 27-week period, in absence of recognized
in two surgical intensive care units (SICUs). All isolates were genotyped by
ld gel electrophoresis analysis. Findings: 18.9% (46/244) of water fitting
arbored P. aeruginosa, and active screening samples from 9.2% (55/595) of
ed patients carried with P. aeruginosa. According to genotype results,
ately 50% of P. areuginosa colonizations/infections of patients were of
s origin. 64.7% (11/17) of exogenous sourced cases were associated with
ated sink traps. There was a significant correlation between the incidence of
s colonization/infection and the prevalence of P. areuginosa in water fitting
(rs ¼ 0.972; p ¼ 0.014). Furthermore, P. areuginosa from sink trap possessed
evel of resistance to multi-antibiotics as opposed to cross-transmission from
ents.
on: Water fitting especially sink trap act as an important role in sporadic P.
a transmission in SICU patients. This report highlights the necessity of
ion of potential environmental reservoirs, such as sinks, for control of
of environmentally hardy multi-resistant P. areuginosa.

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/327119182

Sink-Related Outbreaks and Mitigation Strategies in Healthcare Facilities

Article  in  Current Infectious Disease Reports · October 2018

DOI: 10.1007/s11908-018-0648-3

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Current Infectious Disease Reports (2018) 20:42
https://doi.org/10.1007/s11908-018-0648-3

HEALTHCARE ASSOCIATED INFECTIONS (G BEARMAN AND D MORGAN,
SECTION EDITORS)

Sink-Related Outbreaks and Mitigation Strategies in Healthcare Facilities

Leighanne O. Parkes1 & Susy S. Hota2,3

# Springer Science+Business Media, LLC, part of Springer Nature 2018

Abstract
Purpose of Review In this review, we summarize recent outbreaks attributed to hospital sinks and examine design features and
behaviors that contributed to these outbreaks. The effectiveness of various risk mitigation strategies is presented. Finally, we
examine investigational strategies targeted at reducing the risk of sink-related infections.
Recent Findings Outbreaks of hospital sink-related infections involve a diverse spectrum of microorganisms. They can be
attributed to defects in sink design and hospital wastewater systems that promote the formation and dispersion of biofilm, as
well as healthcare practitioner and patient behaviors. Risk mitigation strategies are often bundled; while they may reduce clinical
cases, sink colonization may persist. Novel approaches targeting biofilms show promise but require more investigation.
Summary Emphasis should be placed on optimizing best practices in sink design and placement to prevent infections. Hospitals
should consider developing a rational surveillance and prevention strategy based on the current design and state of their sinks.

Keywords Sink . Hand hygiene . Hospital-associated infections . Infection control . Biofilm . Multidrug-resistant organisms

Introduction infection control strategies to minimizing the contamination of
hospital sinks and prevent microbial transmission to vulnera-
Since the mid-nineteenth century, when Semmelweis first pro- ble patient populations.
posed that simple handwashing could drastically reduce ma-
ternal mortality, hand hygiene has been a central tenet of in- Here, we review recent outbreaks related to contaminated
fection prevention and control. As an important enabler of hospital sinks, examining specifically design features and
hand hygiene, hospital sinks play an important role in these healthcare provider behaviors that contribute to the transmis-
efforts, and much emphasis has been placed on optimizing sion of sink pathogens. We discuss various risk mitigation
their accessibility in patient care settings. Ironically, hospital strategies that have been employed and their efficacy, with a
sinks are rich microbial breeding grounds and reservoirs for focus on future directions.
the transmission of nosocomial pathogens and resistance
genes [1–3]. Accordingly, it behooves us to define effective Recent Outbreaks of Sink-Related Infections
in Healthcare Facilities
This article is part of the Topical Collection on Healthcare Associated
Infections The relationship between sinks and hospital-associated infection
with hydrophilic organisms has long been described. Over
* Susy S. Hota 40 years ago, epidemiologic studies offered intriguing insights
[email protected] into the transmission of Pseudomonas aeruginosa from sinks to
patients admitted to burn units, where culture-based environmen-
1 Department of Medicine, Division of Infectious Diseases, Jewish tal screening of sink drainage systems demonstrated high colo-
General Hospital, McGill University, Pavilion E-0054, 3755 Chemin nization rates of up to 70.2% [4, 5]. Since then, numerous out-
de la Cote-Sainte-Catherine, Montreal, QC H3T 1E2, Canada breaks have been described, and advances in molecular tech-
niques have strengthened the association between human infec-
2 Department of Medicine, Division of Infectious Diseases, University tions and hospital sinks. Over the past 5 years, there has been an
of Toronto, Toronto, ON, Canada explosion of such outbreak reports, involving an ever-expanding
patient population and pantheon of microorganisms.
3 Department of Infection Prevention and Control, University Health
Network, 9th Floor – 8 PMB 102, 585 University Avenue,
Toronto, ON M5G 2C4, Canada

42 Page 2 of 14 Curr Infect Dis Rep (2018) 20:42

While any water source within healthcare facilities may be bacterial community expands and matures, secreting extracel-
susceptible to colonization with waterborne pathogens, contam- lular polymeric substances, which encase and reinforce the
inated hand hygiene sinks are commonly implicated as the growing colony, trap and concentrate nutrients, and protect
source of outbreaks. These outbreaks most frequently occur in against mechanical and chemical disinfection [50]. The
neonatal and adult intensive care units (ICUs) and burn units, as polymicrobial constituents interact in complex cooperative
well as hematology-oncology and transplant wards (Table 1). and antagonistic ways, resulting in the emergence and transfer
Accordingly, the individuals most commonly affected by sink- of resistance genes and virulence factors [51]. The horizontal
related outbreaks are vulnerable patient populations, including transfer of GIM-1 [52], KPC, NDM [53], and MRSA [54] has
neonates, the critically ill, and immunosuppressed. been demonstrated in hospital sinks.

Waterborne bacteria predominate in sink-related outbreaks, Sink biofilm formation is often enhanced by certain design
with P. aeruginosa being the most commonly identified organ- features, leading to high microbial burden. These features in-
ism. Other pathogens include Enterobacteriaceae, such as clude the use of plastic traps [36••]; faucets with aerators or
Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, other flow modulators [9, 10, 12, 13, 27, 46, 47, 55]; rimmed
Serratia marcescens, Enterobacter species, Citrobacter spe- faucet spouts [7, 36••]; sink rubbers [56]; and overflow holes
cies, and Pantoea agglomerans. Non-fermenting organisms [31]. When biofilm and corrosion deposits are visibly noted
such as Stenotrophomonas maltophilia, Acinetobacter on faucet aerators, P. aeruginosa load in water has been dem-
baumanii, Elizabethkingia meningoseptica, and Burkholderia onstrated to be on average 2-log higher compared to water
species as well as Fusarium species and Mycobacterium from those faucets without aerators [13]. A number of out-
mucogenicum have also been described (Table 1). break investigations cite the presence of biofilm or “slime”
coating these sink features, although the method of detection
Multidrug-resistant (MDR) organisms are featured promi- is most often visual [6, 13, 48, 57]. Other means of biofilm
nently in these reports, with carbapenemases most frequently detection, such as biomass quantification (heterotropic plate
identified. Enterobacteriaceae producing extended-spectrum counts, adenosine triphosphate measurement), visualization of
beta-lactamases (ESBLs) as well as multidrug-resistant P. structure (confocal laser scanning microscopy), and activity
aeruginosa and A. baumanii are also commonly identified. measurements, are more often employed in experimental
The overrepresentation of MDR organisms in outbreak reports models [58–61].
might simply reflect a failure to recognize sink-related trans-
mission of more susceptible pathogens that are not commonly Disruption and Dispersion of Biofilm
included in infection control surveillance. The true burden of
sink-related infections is therefore likely underestimated as Cells within the biofilm can actively detach, reverting back to
there is currently no widespread systematic surveillance strat- their planktonic phenotype or, passively slough as a conse-
egy addressing this type of hospital-associated infection. quence of changes in nutrient availability, chemical disrup-
tion, or aberrations in fluid dynamics [50, 60]. These sloughed
Design Features that Promote Sink-Related aggregates may then transfer to the hands of healthcare
Infections workers and adjacent patient care items such as medications,
medical supplies, or devices or make direct contact with pa-
Sinks are complex items, with multiple fixtures that present a tients, causing infection [61]. Two key sink design features
unique environment for microorganisms (Fig. 1). There are that facilitate such aerosolization, splashing, and/or surface
two main ways that sink design may facilitate the spread of contamination are the depth of the sink basin, and the faucet
pathogens: (1) by promoting formation of biofilm and (2) by positioning relative to sink drain.
encouraging disruption of established biofilm, resulting in
aerosolization, splashing, or contamination of adjacent Basin Depth
surfaces.
Shallow basins are thought to cause cross-contamination of
Promotion of Biofilm hands during handwashing [11] and promote splashing [32,
38, 43] with subsequent contamination of the faucet, sink
Hospital water systems are rife with biofilm [1, 2, 49••]. Sinks, collar, and adjacent surfaces. In their investigation of several
in particular, are susceptible to biofilm formation, as they are clusters of IMP-4 carbapenemase-producing
repositories of gray-water (wastewater without fecal contam- Enterobacteriaceae (CPE) infections in the ICU setting,
ination). Planktonic bacteria, when in the aqueous environ- Kotsanas et al. identified shallow basins in addition to deteri-
ment of a sink, form a biofilm by attaching to and colonizing orating porcelain, and a tap with water flowing directly into
solid surfaces. A multicellular and sessile bacterial community the drain, as all contributing to significant and visible water
forms as the bacteria adopt a quorum-sensing phenotype. The spray [38]. De Gyeter et al. performed air sampling, culturing

Curr Infect Dis Rep (2018) 20:42 Page 3 of 14 42

such Gram-negatives as S. maltophilia, S. marcescens, and piping as resulting in inadequate chlorine residuals and sub-
Pseudomonas species from bioaerosols generated when the sequent colonization of multiple sinks with P. agglomerans,
faucets in their ICU were running. As a consequence of the precipitating an outbreak on a hematology-oncology ward
short vertical distance (20 cm) between the faucet and the [39]. Gormley et al., using a full-scale test rig, modeled the
drain, contamination of the faucet with bioaerosol was postu- aerosolization of Pseudomonas putida through a building as
lated as contributing to their facility’s outbreak [32]. the consequence of empty traps, a defect not uncommon in
many buildings [67••]. More recently, Mair-Jenkins and col-
Faucet Positioning leagues attributed a sustained restaurant Salmonella enteric
ser. Typhimurium outbreak to bioaerosol contamination of a
Water flowing directly into the drain can disrupt established kitchen as the consequence of ineffective traps as well as
biofilm in sink traps, causing pathogens to disperse via the wastewater pooling and biofilm formation [68••]. Although
Venturi-effect. Numerous studies have identified or postulated outside of a hospital environment, this example demonstrates
this mechanism as contributing to outbreaks [6, 9, 14••, 15, that ineffective trap seals may lead to sink contamination.
19, 28, 31, 32, 36••, 44, 55, 62]. Jencson and colleagues used
culture-based methods to demonstrate the dissemination of Healthcare Provider Behaviors that
Candida species from the sink drain onto the basin and sur- Contribute to Infection Transmission
rounding countertops upon coincident water flow [63]. Hota from Sinks
et al. injected fluorescein into sink traps demonstrating spray
of drain and trap contents up to 1 m from the sink during use Healthcare providers can contribute to the colonization of
[64]. Similarly, Starlander et al. injected safranin into their hand hygiene sinks and the transmission of nosocomial path-
sink drains to reveal visible contamination of the basin rim ogens through two means: (1) the misuse of sinks and (2) the
with water running [29]. Kotay et al. employed an experimen- placement of patient care materials proximal to sinks.
tal design, using green-fluorescent protein-expressing E. coli
to elucidate the mechanisms of bacterial dispersal from sinks. Misuse of Sinks
They demonstrated, over the course of 7 days, the extension of
biofilm from colonized P-traps up into the drain at an aston- The disposal of patient wastewater into hand hygiene sinks
ishing rate of 2.5 cm per day and subsequent dispersal of E. may directly introduce pathogens into sink plumbing and onto
coli to the surrounding areas (< 76 cm) with faucet use. They sink fixtures, resulting in colonization. Moreover, antibiotic
also described retrograde colonization of the P-trap from a run off and the organic materials in patient wastewater pro-
common pipe, suggesting that biofilm creep might extend mote resistance in and provide nutrients to existing biofilms.
beyond an individual contaminated sink and into horizontal A recent study has demonstrated that the upward growth of
piping [65••]. biofilm from colonized traps into drains was accelerated by
the addition of nutrient-rich items similar to those frequently
Factors Beyond the Sink disposed down sinks [65••]. Balm and colleagues performed a
root cause analysis in their investigation of a protracted E.
The observation that sinks in patient care areas might be col- meningoseptica outbreak. They describe the disposal of pa-
onized by retrograde biofilm creep has implicated the greater tient secretions and the cleaning of re-useable patient care
network of hospital wastewater systems as sources of sink- items in hand hygiene sinks as significant contributors [46].
related infection [6, 13, 28]. Materials used in hospital piping Sinks subject to such misuse were found to be more likely
should be taken into consideration, given that plastic has been contaminated with E. meningoseptica (odds ratio 4.38, 95%
shown to encourage biofilm formation more than copper or CI 1.68–11.39, p = 0.004). These behaviors persisted despite
stainless steel [66]. Shaw et al. implicated plastic P-traps as directed interventions due to nursing time constraints, as well
one of a number of sink design features that might have con- as the distance between patient rooms and the unit dirty utility
tributed to a high incidence of MDR Gram-negative bacilli room, which was perceived as interfering with workflow [46].
(GNB) infections in their ICU. Given the perceived extent of
contamination through their water system, they adopted a Placement of Patient Care Materials Adjacent to Sinks
“water-safe” program involving the complete removal of hand
hygiene sinks from their ICU to terminate the spread of these The use of surfaces adjacent to hand hygiene sinks for prepa-
organisms [36••]. Defective conditions in water systems, such ration of patient care items or the storage of clean supplies has
as underuse, high temperatures, excessive pressure fluctua- also been identified during outbreak investigations as contrib-
tions, and alterations in flow can lead to trap seal depletion, uting to transmission. During their evaluation of a prolonged
and shearing, thereby magnifying the problem. In a root cause clonal MDR P. aeruginosa outbreak, Salm et al. identified that
analysis, Yablon et al. identified substantial dead-end water

Table 1 Relevant sink-related outbreaks and associated risk mitigation strategies since 2012 42 Page 4 of 14

Reference Organism Sink Molecular Setting Intervention
source method used

Complete Replacement Installation Disinfection Disinfection Pressurized Enhanced Descaling Point- Eliminate
replacement of sink self- with with other steam cleaning of- storage of
of sink components cleaning chlorine use clean
trap solution filters items near
sink

Breathnach P. aeruginosa Drain; PFGE; W√ √ √
et al. [6] (VIM) T-pip- VNTR BICU
e √
Garvey P. aeruginosa √ U √√
et al. [7] Drain PFGE √ √
P. aeruginosa √ √
Garvey Faucet PFGE HO √ U √
et al. [8] P. aeruginosa
P. aeruginosa Drain WGS NICU √ √ √
Davis et al. [9] Aerator N/A NICU √
Mayes et al. P. aeruginosa
(VIM) Drain PFGE ICU √
[10] √
Ambrogi P. aeruginosa Drain; AFLP ICU
(MDR) aera- √
et al. [11] tor qPCR NICU
Knoester
Drain; PFGE W√
et al. [12] aera- PFGE; ICU
tor W
Bedard P. aeruginosa MLST ICU √√
Drain; Rep-PCR
et al. [13] pipes

Aspelund P. aeruginosa Drain √√

et al. [14••] (MBL) Drain

Wendel P. aeruginosa √

et al. [15] (GIM-1)

Salm et al. [16] P. aeruginosa

(MDR)

Johansson P. aeruginosa Drain MLVA; TW Curr Infect Dis Rep (2018) 20:42
Drain PFGE U
et al. [17]
N/A
Vos et al. [18] P. aeruginosa U √
√
(MDR) U
U √√
Schneider P. aeruginosa Trap RAPD-PCR; HO √ U
Drain microarray √
et al. [19]
N/A HO √
Brandt P. aeruginosa √

et al. [20] (CRO)

Diederen P. aeruginosa Drain N/A ICU

et al. [21] (VIM-2)

Guleri P. aeruginosa Pipes; VNTR ICU √
trap N/A HO
et al. [22] (MDR)
Trap
Kossow P. aeruginosa

et al. [23••] (MDR)

Leistner et al. P. aeruginosa Sink Rep-PCR ICU

[24] (XDR)

Liese et al. [25] Trap N/A HO

Table 1 (continued) Curr Infect Dis Rep (2018) 20:42

P. aeruginosa

(MBL)

Clarivet Klebsiella Trap; PFGE ICU √ √U
W √
et al. [26] pneumoniae aera- PFGE NICU √ √ √
PFGE; HO √
(OXA-48) tor ICU √ √ √
MLST √
Maltezou Serratia Drain PFGE ICU √ √ √ √
√ √
et al. [27] marcescens PFGE; ICU √
MLST √ √
Chapuis Enterobacter Drain ICU √ √
PFGE ICU √
et al. [28] cloacae (ESBL)
PFGE HO √
Starlander Klebsiella Drain PFGE
ICU √
et al. [29] pneumoniae Rep-PCR; ICU
MLST IH
(ESBL)
PFGE ICU
Tofteland Klebsiella Drain N/A HO
PFGE; ICU
et al. [30] pneumoniae ICU √
MLST ICU √
(KPC) PFGE PICU √
PFGE ICU
Lowe Klebsiella oxytoca Drain; AFLP ICU √
PFGE ICU
et al. [31] (ESBL) aera- Rep-PCR;

tor MLST
MLST
De Geyter Polymicrobial CPE Drain; N/A
PFGE
et al. [32] trap Rep-PCR

De Jong Klebsiella Drain

et al. [33] pneumoniae

(ESBL)

Leitner Klebsiella oxytoca Drain;

et al. [34] (KPC) over-

flow

Van Oers Polymicrobial Sink

et al. [35] MDR-GNB

Shaw Polymicrobial Trap √ U√ √
√ √√ √
et al. [36••] MDR-GNB √
√ √
Seara Klebsiella Trap U
√
et al. [37] pneumoniae √ √
√ U
(NDM)
√
Kotsanas Polymicrobial CPE Drain

et al. [38] (IMP-4)

Yablon et al. Pantoea Sink

[39] agglomerans

Wolf Polymicrobial Drain

et al. [40] ESBL

Vergara-Lopez Klebsiella oxytoca Trap;

et al. [41] (IMP-8) pipes

Umezawa Acinetobacter Faucet

et al. [42] baumanii

Hong Acinetobacter Faucet Page 5 of 14 42

et al. [43] baumanii

Landelle Acinetobacter Trap

et al. [44] baumanii

Guyot Stenotrophomonas Sink

et al. [45] maltophilia

Balm et al. [46] Aerator

Table 1 (continued) 42 Page 6 of 14

Ashraf Elizabethkingia Aerator Rep-PCR HO √ √
et al. [47] meningoseptica HO √
Faucet; Phylogenic √
Litvinov Mycobacterium drains No further
et al. [48] mucogenicum colonization

Fusarium species √
√
Reference Intervention Outcome Follow-up
√
Breathnach Eliminate disposal patient Reduction No further Reduction √ Ongoing Ongoing Surveillance Environmental
et al. [6] cases colonization √ cases colonization screening
waste cases √
Garvey √ √
et al. [7] √ √ √
√ √ √
Garvey √ √ √
et al. [8] √ √
√
Davis et al. [9] √ √
Mayes et al. [10] √ √ √
Ambrogi √ √ √√
√ √
et al. [11] √√
Knoester √√ Curr Infect Dis Rep (2018) 20:42
√√
et al. [12] √
Bedard √ √

et al. [13] √ √
Aspelund
√ √
et al. [14••] √√ √
Wendel
√ √
et al. [15] √
Salm et al. [16]
Johansson √√

et al. [17] √
Vos et al. [18]
Schneider √

et al. [19] √√
Brandt
√
et al. [20] √
Diederen √√

et al. [21] √√
Guleri

et al. [22]
Kossow

et al. [23••]
Leistner et al. [24]
Liese et al. [25]
Clarivet

et al. [26]

Table 1 (continued) Curr Infect Dis Rep (2018) 20:42

Maltezou √ √ √
et al. [27] √ √√ √ √√
√
Chapuis √ √ √ √√
et al. [28] √ √ √ √√
√ √ √√
Starlander √ √
et al. [29] √ √√
√ √√
Tofteland √
et al. [30] √ √ √√
√
Lowe √
et al. [31] √ √ √√
√ √√
De Geyter √ √
et al. [32] √ √√

De Jong √ √ √√
et al. [33] √
√
Leitner √ √ √√
et al. [34] √ √√
√
Van Oers √√
et al. [35] √
√ √√
Shaw
et al. [36••]

Seara
et al. [37]

Kotsanas
et al. [38]

Yablon et al. [39]
Wolf

et al. [40]
Vergara-Lopez et al.

[41]
Umezawa

et al. [42]
Hong

et al. [43]
Landelle

et al. [44]
Guyot

et al. [45]
Balm et al. [46]
Ashraf

et al. [47]
Litvinov

et al. [48]

U, unidentified; N/A, not available; MLST, multilocus sequence typing; Rep-PCR, repetitive element palindromic PCR; PFGE, pulse-field gel electrophoresis; AFLP, amplified fragment length polymor- Page 7 of 14 42
phism; RAPD-PCR, random amplification of palindromic DNA; VNTR, variable number tandem repeat; MLVA, multiple locus variable number tandem repeat; WGS, whole genome sequencing; qPCR,
quantitative PCR; XDR, extensively drug-resistant; HO, hematology-oncology; W, ward; TW, transplant ward; NICU, neonatal ICU; PICU, pediatric ICU; IH, inter-hospital

42 Page 8 of 14 Curr Infect Dis Rep (2018) 20:42

Fig. 1 Anatomy of a hospital sink and associated nomenclature. *Flow in eliminating sink colonization. A variety of disinfectants,
modulator; §U-bend/P-trap/S-trap/Siphon; ◊outlet/strainer; image administered with varying frequencies, have been evaluated.
courtesy of Bryan Graham Huck Chlorine-containing solutions have been used in concentra-
tions ranging from 250 [33] to 1000 ppm [36••, 37, 69] and
admission to a room with a colonized sink and hemofiltration administered multiple times per day [27, 43], daily [9, 28, 33,
were independently associated with an elevated risk of acquir- 36••, 37, 39, 55, 69, 70], and thrice weekly [12], either alone or
ing the outbreak organism. A process audit revealed that dur- in combination with other biocides [37]. Other chemical disin-
ing hemofiltration, dialysate bags were emptied in and pre- fectants have been applied with limited efficacy, including hy-
pared adjacent to the hand hygiene sinks. Droplet spray during drogen peroxide [31], glucoprotamin [32], acetic acid [14••],
sink use was thought to be contaminating the dialysate bags. amphoteric and cationic surfactants including quaternary am-
After replacing sink traps, implementing single-use bags and monium compounds (QACs) [37, 70], sodium hydroxide [37],
restricting practices around sinks, the incidence of infections and polyhexamethylene biguanide hydrochloride [70]. When
decreased [16]. Ashraf et al. report an outbreak of M. successful, the effect of disinfectants appears to be temporary
mucogenicum bloodstream infections originating from a hand or solely interrupts the outbreak without completely
hygiene sink with a colonized faucet aerator. An audit re- decolonizing the sinks. Garvey et al. report that “descaling
vealed that saline flushes were being prepared on the counter and disinfection” with enhanced routine cleaning was insuffi-
adjacent to the contaminated sink, using a saline bag that was cient to rid hand hygiene sinks of P. aeruginosa in their burn
hung over the sink basin, presumably leading to the contam- ICU, noting recolonization following 102 days [7]. Two other
ination of the flushes [47]. studies highlighted a similar pattern of clearance and subse-
quent re-emergence [38, 46]. Bacteria living in biofilm are able
Infection Control Strategies Used to survive in the presence of 100 to 1000 times higher concen-
During Sink-Related Outbreaks trations of disinfectants than their planktonic counterparts.
They may also limit the penetration of disinfectants, sequester-
Infection control strategies are often bundled together during ing and expelling these agents [71]. The use of disinfectants in
outbreaks, with an emphasis placed upon (1) cleaning and dis- the presence of biofilm can select for resistance, and reduced
infection; (2) biofilm disruption; (3) installation of point-of-use susceptibility to chlorine and QACs has been reported [72].
filters; and (4) the replacement of sink plumbing and/or fixtures. Moreover, the presence of organic residue as well as inade-
It is thus difficult to determine whether a single given interven- quate contact time within the sink environment might contrib-
tion was responsible for successfully interrupting the outbreak, ute to the observed reduced efficacy of these agents.
or if success is predicated upon a variety of interventions.
Biofilm Disruption
Cleaning and Disinfection
Pressurized steam has been employed as an adjunct to chem-
Although many studies fail to describe what products and/or ical disinfection, capitalizing on the thermotoxic effect of high
processes were employed, based upon reported outcomes, it temperatures while also disrupting biofilm. Herruzo et al.
appears that cleaning and disinfection alone is rarely effective achieved clearance of OXA-48 K. pneumoniae from their sink
drains following the application of pressurized steam with a
chlorine-containing solution. However, the effect of their in-
tervention was short-lived, with 50% of sinks recolonized
within 9 months [61]. A similar pattern of temporary clearance
followed by re-emergence was noted in a similar study fol-
lowing a very brief 3 days [38].

Self-disinfecting traps have shown more promise in
disrupting biofilm. These units use vibration, bundled with
heat or ultraviolet radiation to remove existing biofilm, reduce
microbial burden, and prevent further biofilm formation. In
practice, these units may successfully reduce rates of sink-
related hospital-associated infection and/or sink pathogen col-
onization [19, 20, 23••, 40, 72, 73••]. However, the implemen-
tation of self-disinfection traps is often bundled with other
interventions, such as point-of-use filters, plumbing or fixture
replacement, and chemical disinfection. When evaluated
alone, Wolf et al. noted complete interruption of ESBL

Curr Infect Dis Rep (2018) 20:42 Page 9 of 14 42

transmission events as well as sustained negative environmen- their sink drains of P. aeruginosa using weekly 24% acetic
tal cultures at 20 weeks [40]. However, although Fusch et al. acid and hot water flushing, discovered that at 13 weeks fol-
found a reduction in P. aeruginosa clinical cases and sustained lowing sink replacement, the drains once again cultured pos-
lower sink aerosol contamination rates associated with the itive. The organism was detected in multiple wall drainpipes
implementation of self-disinfecting traps, their sinks remained suggesting a deeper reservoir in the horizontal wastewater
contaminated. These units were installed after replacement of system [14••].
the sinks alone failed to achieve a sustained reduction in aero-
sol contamination, raising the possibility of a deeper reservoir In a recent 6-year quasi-experimental study, the inves-
[72]. Although promising, self-disinfecting traps incur sub- tigators explored the effect of the removal of all hand
stantial cost, and they require further evaluation in healthcare hygiene sinks from ICU patient rooms on rates of MDR-
settings. GNB. Although lacking molecular analysis, their inter-
vention was associated with a significant decline in their
Point-of-Use Filters baseline MDR-GNB rates [36••]. A water-free patient care
environment was also explored in an ICU where hand
The resiliency of pathogens in established biofilms has hygiene sinks were removed from patient care areas.
prompted alternative risk mitigation strategies, including the Following their intervention, they observed a significant
installation of point-of-use filters when enhanced cleaning and reduction in GNB colonization in their patients, an effect
disinfection have failed [13, 36••, 48, 74]. Filters are suscep- which was most pronounced in those with long ICU-stays
tible to leaking, saturation requiring frequent changes, and [76••]. Such an intervention could only be considered in a
microbial contamination [7] and may have other disadvan- setting with high hand hygiene compliance rates using
tages such as reduced water pressure [75]. When used, they alcohol-based hand rub as well as low endemic Clostridioides
require a rigorous maintenance program. difficile rates.

Replacement of Sink Plumbing and/or Fixtures Despite attempts at disinfection, the implementation of
biofilm disruption strategies, and complete replacement of
The replacement of sinks and/or sink components has been affected sinks, bacterial pathogens often persist as colo-
employed most successfully as an outbreak mitigation strat- nizers of hospital premise plumbing and fixtures [49••,
egy [9, 11, 12, 19, 21, 22, 26, 27, 30–32, 36••, 37, 42, 43, 77]. This said, a number of these interventions are suc-
69]. However, replacement of individual sink components cessful in terminating transmission of pathogens from
has not been universally effective, or has produced only a sinks to patients and therefore should not be dismissed
temporary effect, suggesting a persistent reservoir in the as ineffective.
retained sink fittings. Despite the replacement of drainpipes,
Bedard et al. noted ongoing Pseudomonas colonization of Investigational Strategies to Mitigate the Risk
the drain and faucet on environmental screening [13]. of Sink-Related Infections
Similarly, even with replacement of faucet aerators, two oth-
er studies reported ongoing microbial colonization of their A number of additional risk mitigation strategies are under
sinks [12, 46]. investigation but have not yet been adequately tested in clin-
ical environments. These include newer methods of biofilm
Complete sink replacement has been reported as effective, disruption and prevention, and resistome modulation.
however, like other risk mitigation strategies, may not always
successfully result in decolonization. Hong et al. attempted Enzymes, such as proteases, DNAses, and polysaccha-
disinfection of MDR Acinetobacter colonized sinks and fau- ride depolymerases, function by dismantling biofilm ma-
cets with sodium hypochlorite five times daily. In the face of trix; when used in conjunction with chemical disinfec-
ongoing environmental colonization and clinical cases, they tants, they may enhance the biocidal effect [78].
proceeded with complete replacement of affected sinks, effec- However, enzyme efficacy is predicated upon the appro-
tively halting the outbreak and rendering the sinks culture priate selection of a mixture of agents targeting the unique
negative for A. baumanii [43]. De Geyter and colleagues and heterogeneous composition of the biofilm matrix be-
eventually proceeded to replacing their sinks after targeted ing treated. As of yet, enzymes have been used effectively
replacement of traps and pipes was unsuccessful, demonstrat- only in laboratory based-experimental models and the
ing complete clearance of CPE from their ICU sinks. food industry [79–81]. Similarly, bacteriophage therapy
However, environmental screening continued to demonstrate is conceptually intriguing given that phages are able to
the presence of hydrophilic GNB, including MDR easily penetrate biofilm matrix, targeting and eradicating
Pseudomonas and Stenotrophomonas species [32]. Similarly, the constituent microorganisms [50]. Bacteriophages are
Aspelund et al., who seemed to have successfully decolonized species-specific, which hinders their use in multispecies
biofilms like those in a hospital environment.

42 Page 10 of 14 Curr Infect Dis Rep (2018) 20:42

Quorum-sensing inhibitors or quorum quenching strategies adhere to current recommended standards. The reasons behind
have been suggested as effective means to prevent biofilm this are likely multifactorial and might simply reflect the age of
formation; however, this research remains very much in its the healthcare facilities and the relative expense of retrofitting. It
infancy [82]. The use of surfaces with antimicrobial properties may also reflect the often overlooked importance of infection
may prevent biofilm formation by limiting microbial burden. prevention and control in healthcare design.
Metals with biocidal properties have been evaluated in
healthcare settings [83]. Copper has been identified as being Currently, the Canadian Standards Association, in alignment
most effective at reducing overall bacterial burden, with stud- with many other national facility design standards like the
ies examining sinks and sink drainage pipes [83, 84]. American Institute of Architects, stipulate that a hand hygiene
However, there is limited high-quality evidence to suggest sink be installed within each inpatient room and no more than
the efficacy of copper alloy in reducing sink-associated infec- 6 m distance from a given patient’s bed [89, 90]. As the presence
tions. Moreover, the longevity of the antimicrobial effects of of hand hygiene sinks remains an essential component in infec-
copper ions in the sink environment and its ability to generate tion prevention and control, our focus should be on optimizing
resistance remains undefined. Silver and selenium nanoparti- sink design to prevent microbial transmission. The standards
cles have similarly been investigated but their efficacy in sinks themselves have been informed by the literature and provide
has not been clearly demonstrated [85, 86]. provisions for a design that discourages formation of biofilm,
minimizes the aerosolization of water from the drain and/or trap,
More recently, ozone has been implemented in sink design and dissuades high-risk behaviors. At minimum, new builds of
as a biofilm prevention strategy. A recent study examined the healthcare facilities should adhere to these standards. Older fa-
efficacy of a stand-alone hand hygiene sink that features an cilities should take stock of their existing design and implement
ozonation cycle designed to prevent biofilm formation in the simple engineering controls that follow the same principles.
drain and trap. Following experimental inoculation of the sink
with Pseudomonas species and Candida auris, complete erad- Beyond design-based prevention methods, infection control
ication of the organisms from the trap was noted at 9 days. The strategies should include “safe water practices.” These should
study failed to demonstrate significant decolonization of either stipulate that hand hygiene sinks be dedicated to handwashing,
the strainer or the remainder of the sink [87]. It is unclear how and that the disposal of patient wastewater in sinks is prohibited.
this system would perform in a hospital setting where well- Moreover, until a safe distance is clearly defined, it is reasonable
established multispecies biofilm might be present in the distal to suggest that the placement of clean supplies or clean work
wastewater plumbing. surfaces within 1 m of hand hygiene sinks be avoided or, alter-
natively, a barrier be installed to protect these vulnerable zones.
A Bacillus-based cleaning strategy has been used to modu-
late the hospital resistome by counteracting the growth of drug- Finally, recognizing that sinks will always contain microor-
resistant surface pathogens [88]. However, no research has eval- ganisms, infection prevention and control programs should con-
uated the introduction of similar, non-pathogenic probiotic or- sider performing a facility-wide risk assessment to determine the
ganisms in an aqueous environment. Moreover, a metagenomics hazard potential of their current sinks, based on design features.
study characterizing the microbiome of hospital shower hoses This will inform the need for enhanced surveillance and/or pro-
identified genes related to disinfectant tolerance and antimicro- active risk mitigation to avoid sink-related outbreaks.
bial resistance amidst the largely non-pathogenic microbes iden-
tified [49••]. More research directed at understanding the com- Conclusion
plexities of biofilm communities is required before a similar risk
mitigation approach is introduced. Hospital sinks provide a permissive environment for biofilm
formation and microbial colonization and sink-related out-
Lessons Learned breaks are increasingly reported over time. The role of hospi-
tal sinks has become even more salient in the era of emerging
These outbreaks have taught us that reactionary responses and antimicrobial resistance, given that CPEs and other MDR-
mitigation strategies are woefully ineffective at eliminating sink GNBs have demonstrated an affinity for this environmental
colonization with clinically significant pathogens and, in some niche. Risk mitigation strategies such as cleaning and disin-
cases, their transmission. Furthermore, the implementation of fection as well as sink replacement have been employed with
policies restricting the use of hand hygiene sinks to handwashing variable success, often halting outbreaks or reducing clinical
is unlikely to be sufficient in isolation. With respect to hospital cases but failing to decolonize the sinks. It is neither reason-
sink-related infections, there is a role for prevention through de- able nor feasible to expect sterility of hospital sinks. Emphasis
sign. Despite the frequent identification of deficiencies in sink should thus be placed on optimizing best practices in sink
design as a primary driver behind sink-related infections, many design and placement, as well as healthcare provider behav-
of the sinks described in recent outbreak investigations do not iors to prevent transmission of potentially dangerous patho-
gens from sinks.

Curr Infect Dis Rep (2018) 20:42 Page 11 of 14 42

Acknowledgements We would like to thank Infection Prevention and 12. Knoester M, de Boer MG, Maarleveld JJ, Claas EC, Bernards AT,
Control construction leads, Jessica Fullerton and Karl Zebarth, for the de Jonge E, et al. An integrated approach to control a prolonged
details they provided regarding the existing national facility engineering outbreak of multidrug-resistant Pseudomonas aeruginosa in an in-
standards. We would also like to thank Ani Orchanian-Cheff for her tensive care unit. Clin Microbiol Infect. 2014;20(4):O207–15.
assistance in performing the literature search and Bryan Graham Huck
for his sink illustration. 13. Bedard E, Laferriere C, Charron D, Lalancette C, Renaud C,
Desmarais N, et al. Post-outbreak investigation of Pseudomonas
Compliance with Ethical Standards aeruginosa faucet contamination by quantitative polymerase chain
reaction and environmental factors affecting positivity. Infect
Conflict of Interest We declare that we have no conflicts of interest Control Hosp Epidemiol. 2015;36(11):1337–43.
relevant to this manuscript. Full disclosures available upon request.
14.•• Aspelund AS, Sjostrom K, Olsson Liljequist B, Morgelin M,
Human and Animal Rights and Informed Consent This article does not Melander E, Pahlman LI. Acetic acid as a decontamination method
contain any studies with human or animal subjects performed by any of for sink drains in a nosocomial outbreak of metallo-beta-lactamase-
the authors. producing Pseudomonas aeruginosa. J Hosp Infection. 2016;94(1):
13–20. This study describes a nosocomial outbreak of drug-
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highlighted as: negative environmental surveillance cultures and appeared to
•• Of major importance halt transmission.

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daily room disinfection, improved hand hygiene practices, and tory use of filtered water from central sinks for daily patient
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