Creation of a cumulative antibiogram for rapidly growing nontuberculous mycobacteria

Reviewed by Michael Payne, MD; London Health Sciences Centre

Nontuberculous mycobacteria are a rare but increasing cause of respiratory and skin/soft tissue infections. They have been previously associated with nosocomial infections and cosmetic procedures. Antimicrobial susceptibility testing for rapidly growing mycobacteria (RGM) is uncommon and typically only performed at reference laboratories. This study created a cumulative antibiogram for 14 RGM using a large number of isolates (N = 3860), over a 3 year period (2018-20) at the National Jewish Health Laboratory. Mycobacterium abscessus complex showed low percentages of susceptibility to most antimicrobials. An intact erm(41) resistance gene was detected in 70% to 100% of M. abscessus abscessus and bolletii. Mycobacterium chelonae had a similar susceptibility pattern to M. abscessus subsp. massiliense except that it was typically susceptible to tobramycin (87%). Mycobacterium fortuitum complex and similar organisms showed higher frequency of susceptibility to fluoroquinolones, beta-lactams, linezolid, and trimethoprim/sulfamethoxazole. This large study informs therapy decisions and assists with monitoring patterns of resistance. It is limited by a larger geographic catchment area, with possible local variations in resistant patters. In addition, referral for testing to this large center may bias towards more resistant isolates being selected for submission and testing.

Reference: Hunkins JJ, et al. In vitro susceptibility patterns for rapidly growing nontuberculous mycobacteria in the United States. Diagn Microbiol Infect Dis. 2023 Mar;105(3):115882.

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