Blog | Wednesday, November 9, 2016

The ineradicable Mycobacterium chimaera


There are two important recent “must-reads” about the global outbreak of Mycobacterium chimaera with a crude mortality rate of about 50%.

Peter Schreiber and colleagues from Switzerland report their experience trying to eradicate M. chimaera from their heater cooler units (HCUs) using an intensified cleaning and disinfection protocol (daily water changes using Pall-filtered tap water and 3% hydrogen peroxide, with biweekly 3% sodium hypochlorite (aka bleach) or paracetic acid disinfection). In that paper, M. chimaera persisted despite this intensified regimen, and cultures frequently skipped between positive and negative (and back again). This study nicely demonstrates the ineradicable nature of M. chimaera colonization in these Sorin 3T units, as well as the poor negative predictive value of a single set of HCU water cultures. Not only does a negative culture not reassure, but it takes 6-8 weeks to return, so cultures are not actionable for management of individual HCUs. Another interesting tidbit from this article is a photo of the “housing unit” that they built to separate the HCU exhaust air from OR air and funnel it directly to the OR exhaust system.

Finally, take a minute to read the best recent news article about this outbreak, from David Weissman at the York Dispatch. I continue to be astonished at the relative lack of media interest in this slow-motion train wreck, but in this piece the reporter clearly understands the potential ramifications of this problem, and touches on a key point: Why hasn't there been more attention to patient notification for those who were exposed to HCUs that we now know were contaminated when they left the factory?

Daniel J. Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. This post originally appeared at the blog Controversies in Hospital Infection Prevention.