The unfolding M. chimaera debacle: June 2016 update

It’s time for some updates about the evolving global outbreak of invasive M. chimaera infections linked to heater-cooler units (HCUs—see prior posts here). Notable developments in June include:

Release of an FDA Safety Alert regarding the Sorin 3T HCU: In this alert, the FDA references the Eurosurveillance study we recently discussed, recognizing the evidence for factory-source contamination of 3T units, stating that “if your facility purchased and used a 3T prior to September 2014, be aware that the units may have been shipped from the factory contaminated with M. chimaera”. FDA now recommends all such facilities (1) inform surgeons about their patients’ infection risk, and (2) “determine a method for patient follow-up and establish patient surveillance” (per CDC recommendations). 

Do you know if your hospital uses the 3T units? If so, are you alerting clinicians and working on a surveillance approach?

Meeting of the FDA Circulatory System Devices panel (June 2-3, 2016): During this meeting, the risks of bio-aerosol generation by HCUs were discussed at length. Slides and other materials from this meeting are here. Although all slide sets are available at this site, a quick 24-hour summary is here. Here are a few of my own random observations from this meeting:

• Awareness of this issue is still very limited, a point made by several panel members who should have already heard about fatal infections linked to HCU bio-aerosol generation. Broader notification is needed.
• HCU models differ dramatically in their design, and in their risk for production of aerosols (for example, the range of air movement by the HCU fans is an astonishing 20->700 cubic feet of air per minute, and the location and containment of the water source also varies). 
• Routine culturing of HCU water for mycobacterial contamination isn't particularly useful and will likely not be recommended outside of outbreaks or clusters of infection. Only a small number of labs can do the cultures properly, negative results can be falsely reassuring, and the cultures take 8 weeks to return. Our own experience confirms this--we've had consecutive samples from the same unit yield different results, as have others. However, routine bacterial cultures ("heterotrophic counts") will continue to be recommended as a monitor for effectiveness of disinfection.
• No obvious near-term solution is evident. Replacement or recall of all 3T units is not possible given that it has 60% market share, and the panel felt that removal of the HCUs from the OR is not practical (despite the fact that some EU countries have done so). A rapidly-implementable engineering solution is desperately needed.

Thus there are undoubtedly many M. chimaera-contaminated 3T units being operated inside ORs, which really is an untenable situation. If your hospital can’t engineer a solution to remove this device from the OR (or otherwise separate the 3T HCU exhaust air from OR air), then you should seek to replace them with other makes/models not linked to this global outbreak. 

Publication of the first US case series of invasive M. chimaera infections. Three cases have been reported from Mayo Clinic, preprint available from OFID here. The cases have similar clinical presentations to those reported already from Europe, and larger case series are undoubtedly to follow. Notably, two of the three patients in the Mayo series died, and the third (a 66 year old with aortic graft infection) is being treated medically due to the risk of graft replacement.

Based upon what I’ve heard from other clinicians caring for these patients, I propose this as an open question: once a patient has a device-associated invasive/systemic infection due to M. chimaera, is cure possible? Given the very long incubation period for this syndrome, this question is not currently answerable. The criteria for cure would require 24+ months without symptoms (and with negative cultures), after device replacement and 18 months of therapy. Stay tuned.

Image: The Chimaera of Arezzo