Hospital water linked to 40 Mycobacterium abscessus cases in UK outbreak investigation

An outbreak investigation at a specialist heart and lung hospital in England began after two lung transplant recipients developed Mycobacterium abscessus three months after the hospital relocated. Investigators screened respiratory samples from transplant recipients and patients with cystic fibrosis or non-CF bronchiectasis, sampled the environment during 2019–2025, and used whole-genome sequencing to compare isolates. Outbreak cases were defined by positive cultures matching the water-associated strain; a nested case-control study assessed risks among transplant recipients.

The abstract reports 40 cases between May 2019 and June 2026: 11 lung transplant recipients, 11 patients with CF, 14 with non-CF bronchiectasis, and four from other groups. Nineteen were diagnosed with non-tuberculous mycobacterial pulmonary disease. No specific risk factors associated with transplant surgery or bronchoscopy were identified. Environmental testing showed persistence and dissemination of the strain throughout the hospital water system.

Following controls including point-of-use filters and biocide treatment, incidence fell from 12.8 to 2.2 cases annually. The authors report no further cases since June 2025, coinciding with a review of enhanced flushing, although the strain was not eliminated from hospital water. These observational findings support continued water-system risk mitigation for vulnerable patients but cannot establish individual measures’ effectiveness. Full text was unavailable, and the reported surveillance endpoint and last-case dates warrant clarification.