Mycobacterium chimaera Infections Associated With Contaminated Heater-Cooler Devices Among Open Cardiac Surgery Patients: A Global Outbreak

Abstract

After the first report of Mycobacterium chimaera infections following cardiac surgery from Switzerland in 2013, more than 100 cases of M. chimaera infections (infective endocarditis, vascular graft infections, sternal surgical site infections etc.) generally involving prosthetic valves, vascular grafts, and left ventricular assist devices have emerged from Australia, Canada, France, Germany, Hong Kong, Ireland, Netherlands, Spain, United Kingdom, and United States of America (USA). M. chimaera infections following cardiac surgery have been attributed to the use of heater-cooler devices (HCDs) which are integral for cardiopulmonary bypass operations. There is not any contact between the HCU water and the patient blood during the operation, but it was shown that these infections are associated with the contamination of the surgical field or the implanted prosthetic device by M. chimaera-containing bioaerosols produced by HCDs. To date, all M. chimaera infections have been attributed to a specific model of HCD, Sorin (Stockert (R)) 3T Heater-Cooler System (LivaNova PLC, London, United Kingdom; formerly Sorin Group Deutschland GmbH, Manich, Germany). These HCDs were most likely contaminated at the manufacturing facility, as M. chimaera has been recovered from in-use Sorin (Stockert (R)) 3T HCUs within hospitals worldwide, from new unused 3T HCUs, and from water samples obtained at the manufacturing site of LivaNova PLC. Whole-genome sequencing confirms that this is a common-source outbreak, with nearly identical isolates found in 3T HCDs and patients from multiple countries. It is therefore likely that most 3T HCDs manufactured over the past decade are contaminated with the same M. chimaera strain. Although HCDs made by other companies have been found to be contaminated with M. chimaera, they have not been associated with the current outbreak. As these Sorin (Stckert (R)) 3T HCDs have been used since 2006, holds 60 and 75% of the market share in USA and Turkey, respectively, and is used in 200 000 and 50 000 surgeries yearly in the USA and Turkey, respectively; the potential for exposure is significant. Although there hasn't been any case report in Turkey by now and the number of cases is very low compared to the huge number of the cardiovascular surgery procedures performed all over the world, the extent of this outbreak is yet unknown and the incidence will likely increase. Diagnosis of HCD-associated M. chimaera infections is challenging as the symptoms of the infection may be nonspecific; the incubation period could be as long as 6 years; mycobacterial blood cultures are not typically performed in immunocompetent patients but are required for the diagnosis; and the knowledge and awareness of the physicians about this organism and its infections is very low at the moment. In the current situation, M. chimaera should be considered in the differential diagnosis of the patients who have infective endocarditis or vascular graft infections and whose routine blood cultures were found to be negative; blood cultures should be taken using bottles that support the growth of the mycobacteria from these patients. The risk of infection in an affected center is currently estimated to be 1/100-1/1000 patients, but is likely variable based upon the types of surgery performed in the center, how centers use their HCDs, cleaning protocols utilized, and the location and orientation of the HCD in the operating room.