Safe water in healthcare premises

In the UK, high profile incidents, specifically those in Northern Ireland, highlighted the link between Pseudomonas aeruginosa, tap water and clinical infection.^{,  ,}  In 2013, the Department of Health (England) published guidance related to the sampling and testing of P. aeruginosa in healthcare premises as well as introducing the role of the water safety group. In this issue of the Journal the articles by Garvey et al., Tissot et al., and Aspelund et al. serve as a timely reminder that the risks associated with P. aeruginosa and contaminated tap water have not yet been sufficiently controlled or even understood. Coincidentally, the Department of Health has recently updated Health Technical Memorandum (HTM) 04-01 which, as reflected in the title of the new document – Safe water in healthcare premises – emphasizes the role of water in nosocomial infections.

A risk-management approach to the safety of water is pivotal in the control of infection and the water safety group should develop a water safety plan that identifies all potential hazards associated with local water distribution and supply. As observed by Kohn in 1967, these need not be limited to contaminated water and its delivery; moist environmental niches may also play a role. Whereas Tissot et al. did not detect P. aeruginosa in the tap water itself, the retention of inherent moisture on a range of medical equipment and surfaces resulted in the development of biofilms that were recalcitrant to the standard decontamination and disinfection protocols being used. Aspelund et al. identified the sink drain as the source of a metallo-β-lactamase (MBL)-producing P. aeruginosa. In this case, the flow of water directly into the waste outlet positioned below may have facilitated the dissemination of MBL P. aeruginosa via aerosols across the ward. The relationship between the tap outlet and the drain and the potential for back (or retrograde) contamination is also recognized by Garvey et al., who highlight the potential for the handwash basin to be used as a sluice – a practice which could lead to persistent contamination and the recontamination of an already cleaned and ‘safe’ handwash station. Tissot et al. demonstrate that improvements or changes in infection control practice(s) can terminate outbreaks. Thus, as highlighted in the new HTM 04-01, the water safety group must work closely with the infection prevention and control teams to prevent dissemination and transmission of environmental micro-organisms. Control strategies may also include the replacement of contaminated taps, sinks and/or traps. However, if a reservoir should persist further back in the drainage pipes, clinically relevant strain(s) may soon reappear. Aspelund et al. detected MBL P. aeruginosa in sinks 13 weeks after they and associated plumbing had been replaced. In this case, weekly treatment of colonized sink drains with acetic acid resulted in negative cultures and terminated transmission, but accidental cessation of the acetic acid treatment resulted in one further clinical case.

It is clear from the approaches taken in all three manuscripts that identification of clinical cases is fundamental to understanding the source and route of transmission, and Tissot et al. provide good evidence for using a novel typing method (double-locus sequence typing) to link clinical and environmental isolates (where conventional methods had failed). However, as stated by Garvey et al., there need to be improvements in the electronic monitoring of both clinical and environmental results to ensure that these links are not missed.