Prevalence and antimicrobial susceptibility pattern of complex isolates in Chongqing, Southwest China.

OBJECTIVES

To investigate the prevalence of complex (MABC), drug resistance characteristics, and the relationship between clarithromycin (CLA) susceptibility and MABC genotype in Chongqing, China.

METHODS

A total of 434 NTM patient isolates were collected between October 2018 and October 2019. Isolates confirmed to be non-tuberculous mycobacteria (NTM) were tested for minimal inhibitory concentrations of antimicrobial agents. In addition, and gene sequences were used to analyze the acquired macrolide resistance and inducible macrolide resistance.

RESULTS

Overall, 17 different NTM species were detected, of which (22.6 %, 91/403) was most prevalent. Amikacin, CLA, azithromycin and cefoxitin exhibited potent activities against MABC organisms, but no significant differences were observed in drug resistance rates between and ( > 0.05). On day 3 of culture, the acquired resistance rate against CLA was 7.4 % (9/121). Of 41 MABC isolates with inducible CLA resistant, 95.1 % (39/41) isolates belonged to the T28 sequevar, while the remaining 4.9 % (2/41) possessed the genotype. All C28 sequevar isolates were sensitive to CLA on day3 and day 14 of culture. Meanwhile, of the 5 T28 isolates with acquired resistance, all possessed 2058/2059 mutations, including 3 isolates with A2058C mutation and 2 isolates with A2059G mutation. While 2 of the 4  isolates with acquired resistance possessed the A2059G mutation, and one isolate possessed the A2058G mutation.

CONCLUSION

and gene could serve as useful markers for predicting macrolide susceptibility of MABC complex isolates.