Guest blogger, Dr Phil Norville (bio below) writes…

Wastewater systems (sinks, showers and more recently toilets) are attracting attention as their role in healthcare associated infections (HCAIs) continues to gathers evidence. In this blog we take a closer look at toilets and their potential role in transmission, as well highlighting some of the current challenges facing healthcare organisations around wastewater management.

I’ve always had a research interest in biofilms and their role in healthcare associated infections (HCAIs), and given biofilms and wastewater go hand in hand; the challenge of keeping wastewater safe has always fascinated me. We are frequently seeing wastewater systems (and biofilms) being linked to outbreaks.

Multidrug resistant Gram-negative bacteria such as Citrobacter, Pseudomonas, Acinetobacter and Klebsiella species commonly cause these outbreaks (typically in venerable vulnerable patients), with outbreaks often lasting for months and even years. A recent publication from Regad et al, (2024) demonstrated that persistent contamination of washbasins with an OXA-48 producing strain of C. farmeri was the source of an outbreak, lasting several years. The only link between the patients affected by the outbreak was that they had stayed in the same room (months apart) and environmental screening confirmed the presence of C. farmeri in washbasin drains. Frequently (as in this case) a real challenge for IPC and microbiology teams is that contamination of wastewater systems by multi drug resistant organisms (MDROs) often persists, despite multiple interventions designed to eliminate it.

Sinks, showers and drains are now well recognised as potential sources of HAI transmission, which isn’t surprising given that they create a perfect environment (moisture, nutrients and protection from external stresses (such as disinfectants)) for bacterial biofilms to thrive. Sinks pose a challenge for healthcare organisations; placement, design, everyday use (correct and incorrect) and what goes down them, are all factors which must be considered when aiming to reduce transmission risk. The study by Garvey et al. (2023) coined the terms the sink splash (Garvey) zone demonstrating just how far and how much equipment could potentially be contaminated by everyday sink usage. A lot of the focus has been on sinks and drains, but is it time for us to be talking about toilets too?  After all toilets are just big drains, aren’t they?

I remember first seeing an abstract presented at ECCMID in 2022, which linked an MDRO outbreak to contaminated wastewater in toilets and it interested me, especially given how necessary and frequently toilets are used! My interest was recaptured recently when reading a paper that examined the impact of toilet lid position (up or down) or viral aerosol spread.   To my surprise the toilet lid position (up or down) made no difference on rates of viral contamination of surrounding surfaces, although decontamination of toilet bowls (with a toilet brush and acetic acid) did result in a drop in rates of cross contamination. The study only examined one acetic acid based disinfectant product. It would be interesting in follow up studies to look at the performance of other disinfectants, such as chlorine, which is commonly used for toilet disinfection. 

Scanning the literature, researchers have been investigating the potential role of toilets in the spread of infection for almost 50 years with Gerba et al. (1975) examining the dissemination of bacteria and viruses in the surrounding environment after toilet flushing. Unsurprisingly there are examples of toilets being linked to outbreaks. An outbreak of an OXA-48 producing K. pneumoniae in a Belgian hospital was linked to contamination of toilet drain water (Hieirman et al., (2022), concluding that common waste water plumbing connecting toilets in different patient rooms was responsible for the spread of infection. Flushing of toilets (contaminated with faeces positive for Clostridioides difficile) can disperse C. difficile up to 25 cm into the air above toilet seats and contaminate surrounding surfaces, so it is easy to see how toilets can serve as a potential source for transmission of MDROs.

Should we be trying to disinfect after every use? As many healthcare organisations have done with sinks do we need to be considering toilet design to reduce aerosol and droplet generation and reduce potential transmission risk? There is also a bigger question to consider; given their function and design, sinks, showers and toilets often share the same drainage how do healthcare organisations keep whole wastewater systems? Is it feasible for healthcare organisations to continuously monitor wastewater systems? What should healthcare organisations use to decontaminate these systems and keep them safe and who should have responsibility for decontaminating them, given that in ideal world decontamination should happen frequently.

It is clear the challenge for healthcare organisations around management of wastewater systems is significant and we need to start thinking about how we can proactively monitor and continuously keep wastewater systems (including toilets) safe to prevent the spread of HCAIs.

References

Best EL, Sandoe JA, Wilcox MH. Potential for aerosolization of Clostridium difficile after flushing toilets: the role of toilet lids in reducing environmental contamination risk. J Hosp Infect. 2012;

Garvey MI, Williams N, Gardiner A, et al. The sink splash zone. J Hosp Infect. 2023;135:154-156.

Gerba CP, Wallis C, Melnick JL. Microbiological hazards of household toilets: droplet production and the fate of residual organisms. Appl Microbiol. 1975;30(2):229-237. doi:10.1128/am.30.2.229-237.1975

Goforth MP, Boone SA, Clark J, et al. Impacts of lid closure during toilet flushing and of toilet bowl cleaning on viral contamination of surfaces in United States restrooms. Am J Infect Control. Published online December 11, 2023.

Heireman L, Hamerlinck H, Vandendriessche S, et al. Toilet drain water as a potential source of hospital room-to-room transmission of carbapenemase-producing Klebsiella pneumoniae. J Hosp Infect. 2020;106(2):232-239. doi:10.1016/j.jhin.2020.07.017

Regad M, Lizon J, Alauzet C, et al. Outbreak of carbapenemase-producing Citrobacter farmeri in an intensive care haematology department linked to a persistent wastewater reservoir in one hospital room, France, 2019 to 2022. Euro Surveill. 2024;29(14):10.2807/1560-7917.ES.2024.29.14.2300386.

Bio

Dr Phil Norville has a PhD in Microbiology and a Masters in Infection Prevention and Control. He worked for 12 years at one of the world’s leading IPC companies, most recently as Clinical and Scientific Director until April 2024 when he started his own independent IPC consultancy, NORVATE Consulting.