Molecular Epidemiologic Investigation of Mycobacterium intracellulare subspecies chimaera Lung Infections at an Adult Cystic Fibrosis Program.

RATIONALE: Outbreaks of nontuberculous mycobacteria (NTM) among people with cystic fibrosis (pwCF) have been reported at CF Centers with conflicting conclusions. Occurrence of NTM at the University of Vermont Medical Center Adult CF Program was investigated.

OBJECTIVES: Utilize the Healthcare-associated Links in Transmission of NTM (HALT NTM) toolkit to investigate healthcare-associated transmission and/or acquisition of NTM among pwCF having genetically similar NTM isolates.

METHODS: Whole genome sequencing (WGS) of NTM isolates from 23 pwCF was conducted to identify genetically similar isolate clusters (≤30 single nucleotide polymorphism differences). Epidemiological investigation, comparison of respiratory and environmental isolates, and home residence watershed mapping were analyzed.

RESULTS: WGS analysis revealed 2 clusters of NTM (Mycobacterium avium and Mycobacterium intracellulare ssp. chimaera) among pwCF. Epidemiologic investigation demonstrated opportunities for healthcare-associated transmission within both clusters. Environmental M. avium isolates from the healthcare setting revealed no genetic similarity to respiratory isolates. However, M. intracellulare ssp. chimaera respiratory isolates revealed greater genetic similarity to a hospital water biofilm isolate than to each other. Neither cluster had all subjects residing in the same watershed.

CONCLUSIONS: This study suggests healthcare-associated transmission of M. avium among pwCF is unlikely at UVMC, but supports healthcare-associated environmental acquisition of M. intracellulare ssp. chimaera. Presence of genetically similar isolates alone is insufficient to confirm healthcare-associated transmission and/or acquisition. The HALT NTM toolkit standardizes outbreak investigation with genetic analysis, epidemiologic investigation, healthcare environmental sampling, and home of residence watershed identification to test the frequency and nature of healthcare-associated NTM transmission among pwCF.