Candida auris is an emerging threat to healthcare facilities worldwide. Recent, worrying, data from the US suggests that prevalence is increasing rapidly. So, we need to make sure we have every prevention base covered to reduce the chances of cross-transmission. C. auris seems to be quite an environmental organism – and a recent JHI study confirms this, showing extended survival on surfaces and tolerance to low concentrations of some biocides.

C. auris survived pretty well over a period of at least 3 weeks, with the lowest count recorded at >2-log. The ability to survive on dry surfaces was exhibited on a range of materials. Survival properties were also tested using planktonic or biofilm-mode cells and, unsurprisingly, biofilm-mode cells survived better on surfaces. The study also includes some in vitro experiments to examine the impact of exposure to sub-lethal doses of sodium dichloroisocyanurate and benzalkonium chloride. Exposure to both biocides resulted in increased tolerance over time. It’s difficult to describe exactly what this is: “Resistance”, “low-level resistance” (as used in the study), or “tolerance”. It’s not clear what the clinical significance of these relatively small reductions in susceptibility to biocides mean in the real world – I suspect that since in-use concentrations are much higher than the doses used in this study, the experiments may not be hugely representative. However, there will also be a concentration gradient of available biocide in real-world settings caused by biofilms, debris on surfaces, and improper application. Interesting, then, to note the new C. auris UKHSA guidance is out for consultation and recommends against the use of quaternary ammonium compound use when disinfecting surfaces potentially contaminated with C. auris, citing equivocal evidence to support their use.

This study reinforces the need to have a keen focus on environmental hygiene in order to effectively prevent the spread of C. auris in healthcare facilities.