Current infection control measures regarding Heater Cooler Units (HCU) in Germany after the mycobacteria chimaera outbreak 2014–2026

Introduction: The 2014–2016 outbreak of cardiac surgery–associated infections with non-tuberculous mycobacteria (NTM) linked to heater-cooler units (HCUs) led to widespread implementation of environmental monitoring and technical/organizational control measures in Germany. We aimed to describe current infection prevention practices, with a focus on ongoing water and air surveillance related to HCUs in German cardiac surgery centres. Method: An anonymous online survey was distributed to directors of all German cardiac surgery departments by the Deutsche Gesellschaft für Thorax-, Herz- und Gefäßchirurgie e.V. (DGTHG). The survey collected administrative information on procedure volumes, HCU types and placement, disinfection practices, and the use and frequency of routine microbiological water sampling for NTM and air sampling in the operating room. No patient-level data were collected. Results: Twelve departments responded, ranging from small (≈300 cardiopulmonary bypass procedures/year) to very large centres (≈2,800/year), and representing major HCU manufacturers used in Germany. During the outbreak phase, all centres introduced routine NTM water sampling (monthly to yearly) and 4/12 also performed routine air sampling every 3–6 months. By 2026, two centres had discontinued water sampling, and most of the others reduced sampling frequency; air sampling was not implemented or was later abandoned in most institutions (only 3/12 continued). Between 2014 and 2016, 4/12 of centres detected NTM in water and 1/12 reported NTM in air samples; in the most recent 12 months, no positive water or air samples were reported. The proportion of centres positioning HCUs outside the operating room increased from 4/12) during the outbreak phase to 5/12 in 2026. Discussion: German cardiac surgery departments report a clear de-escalation of environmental monitoring for HCUs since the initial outbreak response, particularly for air sampling, while technical measures such as positioning exhaust away from the surgical field and, where feasible, locating HCUs outside the operating room have increased. Given persistent reports of HCU water colonization in the literature, continued water monitoring appears reasonable, with reduced intervals (e.g., every 3–6 months) in centres with consistently negative results, and targeted air sampling primarily when NTM are detected in water to support risk assessment and device management.