Objective: To determine molecular mutations in gyrA and gyrB genes and their association with fluoroquinone-resistance among Mycobacterium abscessus isolates from China.
Methods: Antimicrobial susceptibility profile of Mycobacterium abscessus isolates was evaluated for resistance to levofloxacin (LFX) and moxifloxacin (MFX). The quinolone resistant determing regions (QRDR) of gyrA and gyrB genes of all the isolates was sequenced and analyzed.
Results: A total 70 Mycobacterium abscessus isolates were analyzed, including 45 (64%) M. abscessus subsp. abscessus and 25 (36%) M. abscessus subsp. massiliense. Analysis of antimicrobial susceptibility profile showed 97% (n=68) of isolates were resistance to LFX and 14.3% (n=10) of isolates were resistance to MFX. All the MFX-resistant strains were resistant to LFX. Cross-resistance to LFX and MFX was noted in 14.3% (n=10) of isolates. Sequencing analysis revealed that the Ser83Ala substitution in the gyrA gene and Lys447Arg and Ser464Asn substitutions in the gyrB gene were found in all the isolates from both M. abscessus subsp. abscessus and M. abscessus subsp. massiliense. No mutation was found to be associated with cross-resistance of M. abscessus to LFX and MFX in the entire gyrA and gyrB gene.
Conclusions: Our data suggest that there is no clear correlation between the type of mutation in the gene gyrA and gyrB, and the MIC levels of LFX and MFX for resistant M. abscessus strains.