Guest blogger Dr Isabella Centeleghe shares her thoughts on biofilms and sinks in preparation for the next Journal Club (register here).

I have spent the last 3 years investigating the composition, resilience and antimicrobial resistance (AMR) spread within drain biofilms in hospitals, homes and farms piquing my interest in the subject. After attending numerous conferences throughout my postdoc, it is clear that everyone and anyone has either experienced problems with their drains or is currently battling through some!  This paper is very similar to the work we are doing in Cardiff within our European consortium “COMBAT” https://www.combat-amr.com/. It is really important to not only look at disinfection and eradication of drain biofilms, but also what species are the driving force behind resistance and how the drain biofilms are potentially contributing to AMR spread within healthcare environments.

We know that biofilms not only form in U-bends of sink systems, but also on the surface of taps, where water is directly coming from. Several studies highlight the threat of the “splash zone” where water, from a sink, can travel up to 2m around the basin where we often find either medical preparation areas or, patient beds. But the problem doesn’t just start here, water supply and plumbing have a big part to play in biofilm dissemination. Poor structure can lead to the detachment of biofilm material and colonisation further down the line. These biofilms can contain multidrug resistant organisms (MDRO) and are able to transfer AMR genes leading to persistent survival. Problems with drain biofilms are not limited to the healthcare environment where they receive most attention. This manuscript takes samples of biofilm material from the faucet and drains of handwashing sinks in both hospitals and residential facilities in Australia.

In total, Hayward et al. collected 40 biofilm samples from 20 basins, in which they managed to identify 4079 species using Illumina technology. To no particular surprise, Pseudomonadata was the most abundant Phylum (70.9% relative abundance). In residential buildings, Legionella was significantly higher, whereas Staphylococcus was higher in hospitals. The authors measured two main factors; b-diversity which measures how species composition varies across different areas, in this case they have looked at difference in building type and sampling sites. They also looked at a-diversity which refers to species richness within each sample they have taken. To summarise, the authors identified significant differences overall between species composition in hospitals and residential buildings but did not find significant differences between the sampling site overall (faucet vs drain). Overall, 19 potentially pathogenic species were identified, 38 species deemed potentially corrosive and 20 as strong biofilm formers.

Well, what does this all mean for infection control? This whole study highlights the critical issues we have with not only sinks and drains, but potentially plumbing systems. We all know biofilms provide a refuge for MDRO bacteria, and it appears it’s not limited to just our healthcare environments. Many of the species identified in this study are associated with drinking water, which hasn’t even been looked at and are often overlooked in our systems. We know that many HCAI outbreaks are associated with basins and showers and hopefully these types of studies will paint a better picture of the species lurking here, in the hopes that disinfection and cleaning measures can be improved to control levels of pathogens in our water systems. There are limited studies on biofilm composition, but we know they contain diverse communities and are still unclear of the driving factors. With sinks and showers being used constantly, maybe it’s time to start taking seriously disinfectant selection and basin design.