Investigation of Mycobacterium chimaera infections linked to contaminated heater-cooler units in Ireland
Mycobacterium chimaera cardiac infections have been reported internationally and are linked to a clonal strain transmitted by contaminated heater-cooler units (HCU's) that have been distributed across around the world. An investigation of clinical and environmental M. chimaera isolates was conducted to determine whether they can be linked to the global outbreak strain.National retrospective and prospective investigations were initiated to identify cases of M. chimaera infections associated with open heart surgery. Scheduled water sampling associated withof  heater-cooler units from nine cardiac centres was performed and identification of M. chimaera was performed using 16S rRNA gene and ITS sequencing. Whole genome sequencing of M. chimaera isolates was used to assess the molecular epidemiology and strain clonality between clinical and environmental isolates. Four cases of M. chimaera cardiac infections associated with open heart surgery were identified. Environmental testing revealed the presence of M. chimaera in multiple heater-cooler units in seven centres, almost exclusively among Sorin/LivaNova HCU's. Whole-genome sequencing of M. chimaera isolates from four cases and Sorin/LivaNova HCU's were linked to the M. chimaera outbreak strain 1.1. Replacement of Sorin/LivaNova HCU's with Maquet HCU devices reduced the frequency of M. chimaera being isolated.  Strict monitoring of heater-cooler units and prospective identification of patients who may be at risk of M. chimaera infections is on-going. The replacement of Sorin/LivaNova heater-cooler units appears to be an effective method for mitigation of M. chimaera infections associated with cardiac surgery.