Antimicrobial Resistance in Mycobacterium Abscessus Complex Isolated from Patients with Skin and Soft Tissue Infections at a Tertiary Teaching Hospital in Taiwan

Background: Mycobacterium abscessus complex (MABC) is the most common non-tuberculous mycobacterium that causes complicated skin and soft tissue infections (cSSTIs). The selection of antimycobacterial agents for successful treatment of such infections is a critical issue.

Objectives: To investigate the antimicrobial susceptibility patterns of MABC isolates from skin and soft tissue to a variety of antimycobacterial agents.

Methods: Sixty-seven MABC isolates were collected and partial gene sequencing of secA1, rpoB and hsp65 was used to classify them into three subspecies: M. abscessus subsp. abscessus (MAB), M. abscessus subsp. massiliense (MMA) and M. abscessus subsp. bolletii (MBO). The MICs of 11 antimycobacterial agents for these 67 isolates were determined using a broth microdilution method and commercial Sensititre RAPMYCOI MIC plates, as recommended by CLSI.

Results: In total, 28 MAB, 38 MMA and 1 MBO were isolated from patients with cSSTIs at our hospital. Most MABC strains were resistant to ciprofloxacin, doxycycline, imipenem, linezolid, minocycline, moxifloxacin and trimethoprim/sulfamethoxazole. In addition, most MABC strains were intermediately susceptible or resistant to cefoxitin. Eighteen of the 28 MABs and 1 MBO isolate harboured the T28 polymorphism in the erm(41) gene. Two of the 38 MMA isolates had an rrl A2059G point mutation. Most of the MABC strains were susceptible to amikacin and tigecycline.

Conclusions: In Taiwan, amikacin, clarithromycin and tigecycline have good activity against MMA and MAB erm(41) C28 sequevar isolates, whereas amikacin and tigecycline, rather than clarithromycin, have good activity against both MBO and MAB erm(41) T28 sequevar isolates. Clinical trials are warranted to correlate these data with clinical outcomes.