Mycobacterium chimaera found in nearly all heater-cooler units in Denmark, identical to American and British isolates

Following a Rapid Risk Assessment from the European Centre for Disease Prevention and Control (ECDC), associating invasive cardiovascular Mycobacterium chimaera infections with water tanks in Heater Cooler Units (HCUs), all Danish HCUs were investigated; four thoracic surgery departments used Sorin 3T and one used Maquet. M. chimaera was found in all departments, in 86% (18/21) of all HCUs and 75% (14/16) of Sorin HCUs, respectively. Surprisingly, the M. chimaera sequences from the Danish Sorin 3T HCUs were nearly identical (median difference: 3 SNPs; IQR 1-5) to US and UK HCUs as well as similar to Sorin 3T-associated patient isolates (median difference: 6 SNPs; IQR 3-9). Conversely, the Maquet HCU isolate differed significantly from all Sorin 3T isolates (median difference: 48 SNPs; IQR 47-50). In conclusion, M. chimaera was abundant in HCUs in Denmark and strong evidence points to all Sorin 3T-associated M. chimaera having a common source.