Mycobacterium abscessus is a nontuberculous mycobacterium that commonly exhibits antimicrobial resistance and can cause severe disease, particularly among vulnerable patients in healthcare settings. Hospital water systems and plumbing-associated biofilms are recognized reservoirs for nontuberculous mycobacteria and pose a cross-infection risk when patients are exposed.
In June 2024 a cluster of M. abscessus infection cases was reported at a hospital in Maryland, USA. The cluster prompted a coordinated public health and facility-based response to identify sources, characterize transmission, and implement mitigation to prevent further infections.
The investigation involved hospital infection prevention personnel, the Maryland Department of Health, the Centers for Disease Control and Prevention (CDC), and the Wadsworth Laboratory of the New York State Department of Health. The multidisciplinary response combined epidemiologic review, environmental sampling of hospital water and plumbing-associated sites, and molecular testing including whole-genome sequencing of isolates from patients and environmental sources.
Environmental sampling targeted hospital water sources and plumbing fixtures. Patient and environmental isolates underwent whole-genome sequencing to assess relatedness. Sequencing results demonstrated a close genomic relationship between environmental and patient isolates, with differences ranging from 0 to 24 single-nucleotide polymorphisms (SNPs). These genomic data, when integrated with epidemiologic findings, indicated that patient infections were likely linked to exposure to the hospital environment.
During the investigation the hospital and public health partners implemented multiple mitigation measures aimed at reducing patient exposure to water-associated M. abscessus. Interventions described in the report included:
The coordinated rollout of these measures was intended to interrupt ongoing exposure and reduce risk while the investigation and remediation proceeded.
Integration of epidemiologic data with genomic analyses revealed a strong association between environmental and patient isolates, supporting the conclusion that the hospital water environment was the likely source of the cluster. The reported SNP range (0–24) between isolates provided molecular evidence of linkage. The authors state that initiating mitigation efforts during the investigation likely prevented additional patient infections.
This investigation highlights several practical implications for infection prevention teams in hospitals:
The report notes that while the mitigation measures used in this investigation were effective in this circumstance, not all interventions are equally feasible or sustainable long term. Some strategies (for example, prolonged point-of-use filtration or repeated hospitalwide flushing) may pose logistical, financial, or operational challenges for hospitals. The source does not provide detailed comparative effectiveness data or long-term outcomes beyond stating that mitigation likely prevented further infections in this cluster.
A June 2024 cluster of Mycobacterium abscessus infections in a Maryland hospital prompted a multiagency investigation that combined environmental sampling, epidemiology, and whole-genome sequencing. Genomic evidence (0–24 SNP differences) linked patient and environmental isolates, supporting the conclusion that patient exposure to the hospital water environment was the likely source. Rapid implementation of water-based mitigation measures and staff education likely prevented additional infections, but the report emphasizes the challenge of selecting interventions that are both effective and sustainable for routine infection prevention.
Reference details: the investigation is reported in Emerging Infectious Diseases (Sept 2026;32[9]:1397–1401) with PMID 42660585 and DOI 10.3201/eid3209.260093.