Mycobacteriological characteristics and treatment outcomes in extrapulmonary Mycobacterium abscessus complex infections

- Mycobacterial and clinical characteristics of extrapulmonary Mycobacterium abscessus complex (MABC) were studied.
- Fifty percent of extrapulmonary MABC infections were caused by M. abscessus subspecies massiliense.
- Favorable outcomes were associated with M. abscessus subspecies massiliense and M. abscessus subspecies abscessus C28 sequevar.
- Precise subspecies differentiation is important for the treatment of extrapulmonary MABC.

SummaryObjectivesThe differentiation between Mycobacterium abscessus subspecies abscessus (M. abscessus) and Mycobacterium abscessus subspecies massiliense (M. massiliense) and determination of the presence of inducible resistance to macrolide antibiotics are important factors in the management of patients with Mycobacterium abscessus complex (MABC) infections. Unlike pulmonary MABC infections, little information on extrapulmonary MABC infections is available.MethodsThe molecular identification of clinical isolates was performed, and the clinical characteristics and treatment outcomes of 20 consecutive patients with extrapulmonary MABC infections were assessed.ResultsM. abscessus and M. massiliense each caused 10 (50%) of the cases. Eight (80%) M. abscessus isolates that had inducible resistance to clarithromycin harbored an intact erm(41) gene of the T28 variant, whereas two (20%) M. abscessus isolates had the C28 erm(41) variant and were susceptible to clarithromycin. All M. massiliense isolates had a truncated erm(41) gene and were susceptible to clarithromycin. The drug susceptibility profiles other than clarithromycin were similar for the M. abscessus and M. massiliense isolates. Of the 20 patients, 17 (85%) showed a favorable outcome, including all patients with M. massiliense infection and 70% (7/10) of patients with M. abscessus infection. Favorable outcomes were associated with M. massiliense and M. abscessus isolates with a non-functional erm(41) gene (p = 0.049).ConclusionsPrecise species and subspecies identification and the determination of macrolide susceptibility are recommended for the optimal treatment of extrapulmonary MABC infections.