Investigating Drain-Life

Multiple studies have identified that handwash basin, sink and shower drains and ubends play a role in the transmission of healthcare-acquired antibiotic-resistant infections, particularly those caused by Klebsiella spp., Pseudomonas aeruginosa and Escherichia coli. 

The niche environment of healthcare drains and ubends supports biofilm formation and populations, enabling ease of microbial genetic exchange.  Where multi-drug resistant infections have been reported, it is prudent for Infection Prevention to delve into these niches as part of an environmental investigation.  Often such pathogens are intermittent yet persistent in this environment, leading to outbreaks which can span years.

Better understanding of this hazard, the level of risk to patients housed within the same room, and control measures effective in eliminating, mitigating or controlling this risk is needed.  Strategies which remove water sources altogether from patient rooms have been successful in ending outbreaks, reducing background Gram negative infections and reducing antibiotic use.  However, how to manage these risks where water services do remain in place?

Collecting and testing water samples from drain sites is complicated. Care must be taken when collecting ubend aspirates.  Whole genome and metagenomic sequencing can be completed to assess the genetic diversity of microorganisms present.  Metagenomics is the preferred test method to identify individual species from multi-(poly)microbial samples such as those found from sink drains.  As with all water samples, the correct method of sample collection, storage and transport are critical for successful and meaningful results from the lab.

A methodology has been developed and published by the team at John Radcliffe Hospital, Oxford (Constantinides et al., 2020) following their investigation into drain-life.  In summary they found E. coli, Klebsiella oxytoca and K. pneumoniae isolates from sinks in all four wards included in their study (general medicine, adult critical care, acute admissions and haematology) with up to 70% prevalence.  There was genetic similarity between sequenced patient and environmental isolates, and the power of molecular testing presents a picture where isolates are much more widely present than that observed from standard plate culture based screening.  Their paper is detailed with comprehensive genetic analysis, yet their succinct conclusion is that “… we have demonstrated that hospital sink drains are widely—and in many cases abundantly—contaminated with key Enterobacterales species causing healthcare-associated infections and are potential reservoirs of multiple resistance genes encoding resistance to important clinical antimicrobials.”

Screening basin, sink and shower drains is not undertaken routinely, most typically this is only completed during investigation of a known outbreak.  Therefore understanding and quantifying the rate of colonisation and disease risk from drain-derived microorganisms is a knowledge gap.  This John Radcliffe team made a plea for further work to better recognise and reduce risk from drains, and a recent jointly published paper from the University of Oxford, UK Health Security Agency and  Porton Down (Rodger et al., 2024) moves exactly in this practical and preventative direction.

In order to optimise control measures it is critical to understand the environmental drivers supporting critical contamination of healthcare drains and ubends which can encourage and disseminate multi-drug resistant pathogens.  Drivers include antibiotic residues from patient body secretions, blockage and slow flow drainage impacting wastewater systems upstream, poor user behaviours regarding dispose of unused pharmaceuticals, water chemistry and use of sublethal biocide doses.  If analysis can be completed without the need for expensive and/or specialist equipment, a screening and preventative approach may be accessible and adopted.  Where more expensive testing is to be undertaken, then as a minimum the sample condition needs to be optimal, with any deterioration limited.

Rodger and coworkers assessed a variety of commercially available dipsticks to measure the presence of antibiotic residues in hospital sink ubends and water chemistries from hospital tap water.  One of the dipsticks tested was able to detect very low levels of common antibiotics without cross-reactivity nor false-positives.   Another brand of dipstick was better at measuring tap water chemistries. Both offer a quick, cost effective and easy to use “check” for the mysterious water system periphery.

In addition, this study reports on the effectiveness of boric acid to preserve the composition of hospital sink ubend samples during storage and transport prior to metagenomic sequencing.  Samples without boric acid were shown to deteriorate within 48 hours, yet those with boric acid maintained baseline metagenomic readings up to Day 5.  There is a decline between days 2 and 5, therefore preference would be for samples to be tested soonest.

Environmental selection pressures, including presence of antibiotics, in hospital drains and ubends enable the persistence of anti-microbial resistance genes and gene transfer.  Dipsticks are an accessible enabler to detect environmental drivers and coupled with metagenomics an accurate analysis of pathogen and resistance burden in these reservoirs can be measured.  So, how can this be best adopted into practice to both recognise and mitigate risk to patients from their hospital water services?  Share this information with your Water Safety Group and consider if there is a rationale for implementing such test methods in your healthcare facilities under environmental investigation or proactive risk management.  Drains play a critical role in transmitting antibiotic-resistant infections.  Contact our team to explore practical strategies for managing drain-life risks effectively.


Constantinides B, Chau KK, Quan TP, Rodger G, Andersson MI, Jeffery K, Lipworth S, Gweon HS, Peniket A, Pike G, Millo J, Byukusenge M, Holdaway M, Gibbons C, Mathers AJ, Crook DW, Peto TEA, Walker AS, Stoesser N. Genomic surveillance of Escherichia coli and Klebsiella spp. in hospital sink drains and patients. Microb Genom. 2020 Jul;6(7):mgen000391. doi: 10.1099/mgen.0.000391. PMID: 32553019; PMCID: PMC7478627.

Rodger G, Chau K, Aranega-Bou P, Roohi A, Moore G, Hopkins KL, Hopkins S, Walker AS, Stoesser N. A workflow for the detection of antibiotic residues, measurement of water chemistry and preservation of hospital sink drain samples for metagenomic sequencing. J Hosp Infect. 2024 Feb;144:128-136. doi: 10.1016/j.jhin.2023.11.021. Epub 2023 Dec 23. PMID: 38145816.

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