Prolonged Outbreak of Mycobacterium chimaera Infection After Open-Chest Heart Surgery

Background. InvasiveMycobacterium chimaera infections were diagnosed in 2012 in 2 heart surgery patients on extracorporeal circulation. We launched an outbreak investigation to identify the source and extent of the potential outbreak and to implement preventive measures. Methods. We collected water samples from operating theaters, intensive care units, and wards, including air samples from operating theaters. Mycobacterium chimaera strains were characterized by randomly amplified poly-morphic DNA polymerase chain reaction (RAPD-PCR). Case detection was performed based on archived histopa-thology samples and M. chimaera isolates since 2006, and the patient population at risk was prospectively surveyed. Results. We identified 6 male patients aged between 49 and 64 years with prosthetic valve endocarditis or vas-cular graft infection due toM. chimaera, which became clinically manifest with a latency of between 1.5 and 3.6 years after surgery. Mycobacterium chimaera was isolated from cardiac tissue specimens, blood cultures, or other biopsy specimens. We were able also to culture M. chimaera from water circuits of heater-cooler units connected to the cardiopulmonary bypass, and air samples collected when the units were in use. RAPD-PCR demonstrated identical patterns among M. chimaera strains from heater-cooler unit water circuits and air samples, and strains in 2 patient clusters. Conclusions. The epidemiological and microbiological features of this prolonged outbreak provided evidence for the airborne transmission of M. chimaera from contaminated heater-cooler unit water tanks to patients during open-heart surgery