Mycobacterium avium and Mycobacterium abscessus complex target distinct cystic fibrosis patient subpopulations.

BACKGROUND: Clinical observations suggest that Mycobacterium avium complex (MAC) and Mycobacterium abscessus complex (MABSC) may affect cystic fibrosis (CF) patients with different characteristics and risk factors, but this has never been demonstrated within a single prospective cohort.

METHODS: We studied 50 MABSC-positive and 23 MAC-positive patients from a French prevalence study of non-tuberculous mycobacteria (NTM) in CF. Risk factors specifically associated with MABSC and MAC were analyzed by nested case-control studies, with two NTM-negative controls matched by age, sex and center for each case.

RESULTS: MAC-positive patients were significantly older than MABSC-positive patients (mean [SD] age, 23.1 [10.2] vs 17.4 [8.3] years, p=0.013), and were also older at CF diagnosis (mean [SD] age, 12.9 [16.1] vs 3.1 [7.7] years, p=0.015); they tended to be less frequent of the ΔF508/ΔF508 genotype (33.3 vs 61.1%, p=0.17) and to use pancreatic extracts less frequently (82.4 vs 97.6%, p=0.07). Risk factors identified by multivariate analysis were: i) in the MAC case-control study, an older age at CF diagnosis (p=0.004); ii) in the MABSC case-control study, at least one course of intravenous antibiotics (p=0.01) and more frequent isolation of Aspergillus (p=0.03).

CONCLUSIONS: MAC affects adult patients with a mild form of CF, whereas MABSC affects younger patients with more severe CF and more frequent intravenous antimicrobial treatment.