The Global Outbreak of M. chimaera Infection Following Cardiac Surgery: Another Piece of the Puzzle

Invasive cases of <i>Mycobacterium chimaera</i> have been found in Europe, and beyond, and have been associated with the use of heater-cooler units necessary to regulate the temperature of blood in extracorporeal circulation during cardiac surgery, mostly due to contamination of patients by aerosol coming from the water in the tanks of the devices. An outbreak of five cases of <i>M. chimaera</i> infection associated with heater-cooler units Stockert 3T (LivaNova) was also identified in the Piedmont region (Italy). <i>M. chimaera</i> strains isolated from 10 Stockert 3T heater-cooler units used in 3 regional cardiac surgery operating rooms were subjected to whole-genome sequencing. The results were analysed according to van Ingen's criteria. <i>M. chimaera</i> was isolated from 59% of heater-cooler units Stockert 3T (LivaNova) monitored. By whole-genome sequencing analysis performed on <i>M. chimaera</i> strains obtained from 10 heater-cooler units, four strains were classified as subgroup 1.1 or 1.8, which are the two subgroups associated with the HCU-related outbreak worldwide. Our data and their comparisons with global heater-cooler unit isolates provide further evidence of the hypothesis that contamination occurs at the production site of LivaNova following exposure to <i>M. chimaera</i>-contaminated factory plumbing systems.