More data support a common source for the M. chimaera outbreak

As we’ve suggested here and here, the information to this point strongly suggests that the M. chimaera outbreak linked to heater-cooler units (HCUs) is a “common source” outbreak, which has major implications for outbreak response. 

Another piece of the puzzle was published today by Haller and colleagues in Eurosurveillance. Read the whole thing for details of the German outbreak investigation, but the key additional findings are in the table above—brand new HCUs, and the water source at the manufacturing facility, grew M. chimaera. The genome-sequencing results are not included in this report, but read this key paragraph from the discussion below:

"Preliminary typing results indicate that the M. chimaera isolates detected by the authorities and the isolates from the manufacturer appear to be almost identical (unpublished data). The M. chimaera-positive environmental samples at the manufacturing site prompted the manufacturer to modify the manufacturing process, which now includes ethanol disinfection and an active drying of the HCU water circuit before shipment. ……According to the information provided by the manufacturer, HCUs manufactured before mid-August 2014 may have had environmental mycobacteria presence in the unit at the time of delivery [emphasis mine]. Our investigations could not elucidate if and until when contaminated HCUs may have been delivered to customers from this manufacturer." 

It is, of course, impossible to know for how long units were shipped “pre-contaminated” from this manufacturing site to users, but this now-published information only increases the rationale for removal of these HCUs from the operating room. Both Dutch and German authorities took this step, as the authors note. The US should as well—it shouldn’t take long to determine the impact on HCU function of extending the tubing sufficiently to allow this.