Mycobacteroides abscessus Outbreak and Mitigation in a Cardiothoracic Transplant Population: The Problem with Tap Water.

Background: Hospital outbreaks caused by Mycobacteroides abscessus complex are a major cause for concern in vulnerable patients such as the cardiothoracic transplant population.

Aim: To describe the outbreak investigation and mitigation steps undertaken to address an increase in healthcare-associated Mycobacteroides abscessus (M. abscessus) complex cases in an inpatient cardiothoracic transplant population.

Methods: We extracted clinical characteristics from patients with M. abscessus pre-outbreak (March 2018 - December 2020) and during the outbreak (January 2021 - June 2022) from the electronic medical record. A multidisciplinary team conducted the outbreak investigation and devised a mitigation strategy to implement at our institution.

Findings: The baseline incidence of healthcare-associated M. abscessus was 0.11 cases per 10,000 patient-days; this increased to 0.24 cases per 10,000 patient-days during the outbreak. There were 1/9 (11%) cardiothoracic transplant patients in the pre-outbreak group compared to 7/12 (58%) during the outbreak, and respiratory specimen types compromised 6/9 (67%) of M. abscessus results in the pre-outbreak group compared to 10/12 (83%) during the outbreak. Among the clinical care activities involving water, a variety of water sources were utilized, including filtered and tap water. The incidence of healthcare-associated M. abscessus subsequently decreased to 0.06 cases per 10,000 patient-days after implementing an outbreak mitigation strategy of sterile water precautions.

Conclusion: Robust educational efforts from a multidisciplinary team on eliminating exposure to tap water were effective measures to reduce healthcare-associated M. abscessus incidence at our institution. NTM infection surveillance, targeted education, and water mitigation strategies may be beneficial preventative strategies for other lung transplant centres facing similar issues.