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BACKGROUND: An urgent UK investigation was launched to assess risk of invasive Mycobacterium chimaera infection in cardiothoracic surgery and a possible association with cardiopulmonary bypass heater-cooler units following alerts in Switzerland and the Netherlands. METHODS: Parallel investigations were pursued: i) identification of cardiopulmonary bypass-associated M. chimaera infection through national laboratory and hospital admissions data linkage ii) cohort study to assess patient risk iii) microbiological and aerobiological investigations of heater-coolers in situ and under controlled laboratory conditions iv) whole genome sequencing of clinical and environmental isolates. RESULTS: Eighteen probable cases of cardiopulmonary bypass-associated M. chimaera infection were identified, all except one adults. Cases had undergone valve replacement in 11 hospitals between 2007-2015, a median 19 months prior to onset (range 3 months-5 years). Risk to patients increased after 2010 from <0.2 to 1.65/10,000 person-years in 2013, a nine-fold rise for infections within 2y of surgery (RR=9.08, 95% CI 1.81-87.76). Endocarditis was the most common presentation (n=11). To date, 9 cases have died. Investigations identified aerosol release through breaches in heater-cooler tanks. M. chimaera and other pathogens were recovered from water and air samples. Phylogenetic analysis found close clustering of strains from probable cases. CONCLUSIONS: We identified low but escalating risk of severe M. chimaera infection associated with heater-coolers with cases in a quarter of cardiothoracic centres. Our investigations strengthen aetiological evidence for heater-coolers' role in transmission and raise the possibility of an ongoing, international point-source outbreak. Active management of heater-coolers and heightened clinical awareness are imperative given the consequences of infection.

Original publication

DOI

10.1093/cid/ciw754

Type

Journal article

Journal

Clin Infect Dis

Publication Date

07/12/2016

Keywords

Aerosol Release, Cardiac Surgical Procedures., Disease Outbreaks, Equipment Contamination, Nontuberculous Mycobacteria