Clinical and operational impact of a four-year-long bronchoscopy-associated pseudo-outbreak of <i>Mycobacterium mucogenicum</i>

Abstract Objective: To report on the investigation of a pseudo-outbreak of Mycobacterium mucogenicum and examine its clinical and operational impact. Design: Outbreak investigation, retrospective cohort study. Setting: Academic medical center in Los Angeles, California. Patients: Patients whose bronchoalveolar lavage (BAL) cultures grew M. mucogenicum from 2020–2024. Methods: We performed an institutional outbreak investigation of M. mucogenicum , reviewed electronic medical records of a subset of affected patients (2023–2024), and assessed the operational impact. Results: The incidence of M. mucogenicum in BAL cultures at Hospital A increased from 6.1% (29/473) in 2020 to 18.6% (29/156) in the first quarter of 2024. Epidemiologic investigation revealed non-sterile ice baths used to cool uncapped sterile syringes during bronchoscopy procedures as the contamination source. Next generation sequencing linked clinical isolates to M. mucogenicum recovered from a perioperative ice machine. Nearly all (157/160) clinical isolates grew from nocardia media rather than acid-fast bacilli media. Among 154 patients, including 51 (33.1%) who were highly immunocompromised, no true infections were identified. Thirty-nine (25.3%) patients were referred to infectious diseases for consultation, seven (4.5%) underwent additional workup, and only one received targeted treatment. The pseudo-outbreak incurred 458 hours of microbiology technologist and infection preventionist time and cost the laboratory $88,426. Conclusions: A four-year pseudo-outbreak of M. mucogenicum traced to contaminated ice baths used during bronchoscopy resulted in unnecessary infectious disease referrals and substantial operational and financial burden to the institution. Avoidance of non-sterile ice use in procedures prevents costly and burdensome pseudo-outbreaks of environmental mycobacteria in healthcare settings.