Mycobacterium chimaera update: A “must listen” from ECCMID
Fortunately, Dr. Jakko van Ingen gave an excellent talk at ECCMID that answers several important questions we’ve had about this outbreak, confirming some of the things we’ve heard (“in confidence”, I assume for political or legal reasons) on various conference calls and email strings. I urge you to take 30 minutes of your time to listen to his talk, all the way to the end of the Q&A period.
Aside from being an extremely entertaining speaker, Jakko addresses several key questions, including:
- Is this a clonal outbreak? YES. Slide 29 reports whole genome sequencing data that clusters the isolates from Sorin 3T units and infected patients (within just 2-3 SNPs), and further discussion (during Q&A session) confirms that isolates from other European countries are also in this cluster.
- Were the HCUs already contaminated prior to being shipped to end users? YES. Listen carefully to the last question and answer.
- Does this particular outbreak primarily involve one make/model of HCU? YES. While nontuberculous mycobacteria have been isolated from other types of HCUs, the specific M. chimaera cluster in this case involves Sorin 3T units.
- Is the invasive, disseminated, high crude mortality form of the illness restricted to those patients with implants (e.g. valves, grafts)? YES. The life-threatening disseminated infection appears to require some prosthetic material to which the organism can adhere, protecting itself (via biofilm formation) from host defense. According to Dr. van Ingen, case finding in the Netherlands is now limited to those with implants, and does not include standard non-valve, non-implant CABG patients.
- Is it possible to mount an effective, rapid national response to this urgent problem? YES. Slide 18 details the Dutch response, which involved discontinuing all non-urgent cardiac surgery until HCUs were placed outside of ORs (which was done within 48 hours). As we learned here when we did the same thing, it is amazing what you can accomplish when you are left with no other option.
- Is opening up a Sorin 3T HCU a frightening experience? YES. I’m sure I’ll have nightmares about these water-stained, biofilm-befouled devices for a long time (see below for one image from Garvey, et al).
What are the implications?
- HCUs are not safe to operate in an OR. The air exhausting from the HCU ventilation fan must be physically separated from the air in the OR, and the easiest way to do that is to remove them from the OR (and maintain the OR at positive pressure, of course).
- Everyone using Sorin 3T HCUs should assume that they may have exposed patients to M. chimaera, until more is known about the details of the point-source. Contaminated units cannot be disinfected even with the more intensive protocols currently recommended. In addition, only a few labs are capable of properly performing NTM cultures of water samples, so negative water cultures are of limited value and could be falsely reassuring.
- A much more active national patient and provider notification is needed. Our experience is similar to that of others: identified cases would never have been found had it not been for aggressive and active case-finding. There are undoubtedly others currently being treated with immunosuppression for sarcoidosis or some other “granulomatous process of uncertain etiology” who actually have undiagnosed disseminated M. chimaera disease.
Below I've pasted an epidemic curve of non-tuberculous mycobacteria (NTM) cases linked to HCUs (inclusive of M. chimaera, but also isolates not identified to species level and other NTM such as rapid-growers), including cases reported to FDA from US (blue bars) and abroad (red). This outbreak isn't over, and the fact that there are still hospitals performing cardiac surgery with their Sorin 3T HCUs inside of the OR is extremely distressing.