Hospital Environment-Associated Sources of Mycobacterium abscessus Infection in Transplant Recipients

Mycobacterium abscessus (MAB) can cause severe infections in transplant recipients and immunocompromised patients and is frequently associated with health care settings, but the transmission pathways and environmental reservoirs that contribute to these infections remain poorly defined. This knowledge gap limits our ability to prevent and control health care-associated MAB infections in vulnerable patient populations.

To determine routes of transmission of MAB by whole-genome sequencing MAB isolates from patients and health care environmental reservoirs and determining the genetic relatedness of the isolates.

In this cohort study, between October 2019 and January 2025, MAB isolates were collected from patients and patient-associated health care environments, including tap water, sink basins, P-traps, heater-cooler devices, and air, in a tertiary care hospital in North Carolina. Patients with at least 1 extrapulmonary MAB isolate during the study window were included.

Health care environment-acquired MAB infection.

The primary outcome was identification of the environmental sources of health care-associated MAB infections, measured by genomic relatedness between patient and environmental isolates using whole-genome sequencing. Relatedness was quantified as pairwise single-nucleotide variation (SNV) differences, with genomic clusters defined a priori using a threshold of up to 25 SNVs to indicate likely recent transmission.

In total, 41 MAB isolates were obtained from 24 patients, and 54 isolates were obtained from patient-associated health care environments. The MAB isolates from 24 surgical patients formed 4 genomic clusters specific to individual hospital units, and the clusters included environmental isolates from the same units. Only tap water isolates clustered with patient strains, whereas samples from other environmental sources were either culture negative or genetically unrelated. MAB subspecies massiliense was predominant, accounting for approximately 50% of patients' infections. All MAB subspecies massiliense isolates belonged to dominant circulating clone (DCC) 7, which has persisted in the hospital for at least 2 decades. DCC7 is a globally disseminated clone but is most frequently isolated along the US East Coast.

In this cohort study of patients with MAB, the results implicated tap water in patient care units as the likely source of MAB infections and showed that most strains infecting patients belonged to emerging DCC7. These findings highlight the importance of integrating environmental investigation and genomic analysis to identify mechanisms of MAB acquisition in health care environments. Careful water management protocols have potential to prevent health care-associated MAB infections.