Antibiotic Sensitivity Testing and Molecular Characteristics Related to Clarithromycin and Amikacin Resistance in Mycobacterium abscessus Complex Isolated from Patients with Pulmonary Infection at National Hospital 74, Vietnam.

Background: Mycobacterium abscessus complex (MABC) is an important cause of opportunistic infections in the respiratory tracts. Data on antimicrobial resistance of MABC in Vietnam were still lacking.

Methods: From December 2021 to July 2022, mycobacteria growth indicator tube (MGIT) culture and hsp65 gene sequencing were conducted to identify nontuberculous mycobacteria (NTM) from patients with respiratory infections at National Hospital 74, Vietnam. Finally, 123 NTM trains were retrieved. Out of them, 40 MABC were identified and tested for susceptibility to isoniazid, rifampicin, streptomycin, ethambutol, amikacin (AK), moxifloxacin, clarithromycin (CLR), and linezolid (LZD). DNA sequencing of erm (41), rrl, and rrs genes was performed on all CLR-resistant strains and one CLR-susceptible strain (as control).

Results: All 40 MABC strains, including 23 M. abscessus subsp. massiliense (M. massiliense), 16 subsp. abscessus (M. abscessus), and one subsp. bolletii (M. bolletii) were resistant to first-line antituberculosis drugs. Susceptibility was 40/40 in AK and 38/40 in LZD. For CLR, 24/40 strains were susceptible (23 M. massiliense, one M. abscessus). Of 16/40 strains that resisted with CLR, one M. bolletii and 14 M. abscessus exhibited inducible resistance and one M. abscessus had acquired resistance. All 16 CLR-resistant strains carried erm (41) T28 genotype, and the CLR-susceptible M. abscessus strain had T28C. No mutations associated with AK and CLR resistance were found in rrs and rrl genes.

Conclusions: Inducible CLR resistance was predominant, associated with erm (41) T28 genotype. AK and LZD appear to be promising for the treatment of MABC. CLR remains effective against M. massiliense but is less suitable for treating M. abscessus.