Enterococcus faecium, VRE and alcohol tolerance

Paul D.R Johnson1

1Austin Health & University of Melbourne, Heidelberg, Victoria, Australia.


Programs promoting alcohol based hand hygiene and cleaning of shared items in hospitals, often using waterless products such as alcohol wipes, were pioneered in Australia at Austin Health and have been increasingly adopted in other Australian hospitals since then. This has resulted in marked reductions in hospital acquired infections, particularly those due to methicillin resistant S. aureus (MRSA). Paradoxically, there have been unexplained increases in hospital acquired Enterococcus faecium VRE infections in Australian hospitals starting from the mid-2000s. At Austin Hospital in Melbourne, where hospital acquired MRSA-bacteraemia is now rare, VRE has proved more difficult to control despite high levels of compliance with standard precautions and alcohol based hand hygiene. Fortunately, VRE has proved considerably less virulent than MRSA. In a collaborative research project using stored blood culture isolates, researchers at the Peter Doherty Institute, Austin Health and Monash Health identified a new phenomenon of alcohol tolerance in clinical isolates of E. faecium including VRE that has appeared progressively over the last 20 years. However, all isolates tested remain fully sensitive in vitro at 70% (the usual concentration of alcohol in hand hygiene products) and we were only able to detect tolerance using a 23% v/v in vitro killing assay. To investigate whether this phenomenon may be of clinical relevance or was just a laboratory curiosity, we undertook a mouse colonisation experiment we called “mouse hospital”. We were able to show that 70% isopropyl alcohol wipes were less effective against tolerant strains of Enterococcus faecium compared with fully sensitive strains in this mouse colonisation model. The paper describing our research was published in Science Translational Medicine in August 2018 and has generated much interest and some criticism. In this presentation our results will be reviewed in outline and possible implications for infection control practitioners discussed. Alcohol based hand hygiene remains a key component of our infection control program at Austin Health.

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