Outcomes of non-tuberculous mycobacterial infection of the bone, joint and soft tissue: a seven-year multicentre retrospective study

Abstract Purpose Extrapulmonary nontuberculous mycobacterial (EPNTM) infections of bone, joint, and soft tissue are difficult to treat and lack species-specific outcome data. We sought to describe antimicrobial regimens and surgical management by Mycobacterium spp. and to identify predictors of a clinical cure within 12 months in this adult cohort with EPNTM. Methods We conducted a multicentre retrospective cohort study across five tertiary hospitals in Australia and New Zealand 2014–2020. Adults with culture-confirmed EPNTM infection from sterile or intraoperative specimens were included. Primary outcome was clinical cure at 12 months. Secondary outcomes included relapse, drug toxicity and host factors. Results Among 107 patients, six species groups were identified, most commonly M. abscessus complex ( n = 26, 25%), Mycobacterium marinum ( n = 25, 24%), and M. fortuitum complex ( n = 24, 23%). Clinical cure within 12 months differed significantly by species, with high cure proportions for M. abscessus complex ( n = 22, 92%) in surgically accessible infections and lower cure rates for M. chelonae ( n = 6, 60%) and amalgamated slow growing mycobacteria ( n = 4, 36%). Younger age (median 47 vs. 60 years, p = 0.006) and Mycobacterium spp. was associated with cure whereas antimicrobial class and surgical intervention were not. Of antibiotic classes used, only macrolide duration was associated with cure. Relapse was uncommon (8%) and occurred predominantly in immunosuppressed patients. Conclusions This first multicentre Australasian cohort demonstrates substantial species-specific variation in outcomes of EPNTM osteoarticular and soft-tissue infections. This study highlights the need for species-specific management pathways and prospective studies.