Treatment of Mycobacterium abscessus complex pulmonary disease

Background: In South Korea, bacteria in the Mycobacterium abscessus complex (MABC), a group of rapidly growing mycobacteria, are second to those in the Mycobacterium avium complex as a cause of non-tuberculous mycobacterial pulmonary disease. The MABC includes several subspecies, including M. abscessus subsp. abscessus (M. abscessus) and M. abscessus subsp. massiliense (M. massiliense), the former of which is difficult to treat owing to its antibiotic resistance.Current Concepts: M. abscessus encodes a functional erythromycin ribosomal methylase gene, erm(41), that causes inducible macrolide resistance. Contrastingly, M. massiliense lacks a functional erm(41) gene owing to a partial deletion. Accordingly, culture conversion rates using currently recommended macrolide-based antibiotic treatments are considerably higher among patients with M. massiliense infection than in those infected with M. abscessus. Phase therapy (intensive and continuous) is recommended for MABC pulmonary disease and, depending on the subspecies and antimicrobial susceptibility test results, should include an initial treatment of ≥3 to 4 injectable and oral antibiotics, followed by inhaled or intravenous amikacin and ≥1 to 2 oral antibiotics. Recommended injectable antibiotics include amikacin, imipenem or cefoxitin, and tigecycline, and oral antibiotics include macrolides (azithromycin or clarithromycin), clofazimine, linezolid, and rifabutin. For some patients, surgery should be considered as an adjunctive treatment option.Discussion and Conclusion: Given that M. abscessus expresses the inducible resistance gene erm(41) associated with macrolide resistance, the identification of MABC subspecies is important for disease management. However, despite the combined application of several injectable/oral antibiotics, the treatment outcomes for M. abscessus pulmonary disease remain unsatisfactory.