• Hugo Sax, Guido Bloemberg, Barbara Hasse, Rami Sommerstein, Philipp Kohler, Yvonne Achermann, Matthias Rössle, Volkmar Falk, Stefan P Kuster, Erik C Böttger, and Rainer Weber.
• Division of Infectious Diseases and Hospital Epidemiology, University Hospital Zurich.
• Clin. Infect. Dis. 2015 Jul 1; 61 (1): 67-75.

BackgroundInvasive Mycobacterium 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.MethodsWe 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 polymorphic DNA polymerase chain reaction (RAPD-PCR). Case detection was performed based on archived histopathology samples and M. chimaera isolates since 2006, and the patient population at risk was prospectively surveyed.ResultsWe identified 6 male patients aged between 49 and 64 years with prosthetic valve endocarditis or vascular graft infection due to M. 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.ConclusionsThe 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.© The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

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