Investigation of bedaquiline resistance and genetic mutations in multi-drug resistant Mycobacterium tuberculosis clinical isolates in Chongqing, China.

Background: To investigate the prevalence and molecular characterization of bedaquiline resistance among MDR-TB isolates collected from Chongqing, China.

Methods: A total of 205 MDR-TB isolates were collected from Chongqing Tuberculosis Control Institute between March 2019 and June 2020. The MICs of BDQ were determined by microplate alamarblue assay. All strains were genotyped by melting curve spoligotyping, and were subjected to WGS.

Results: Among the 205 MDR isolates, the resistance rate of BDQ was 4.4% (9/205). The 55 (26.8%) were from male patients and 50 (24.4%) were new cases. Furthermore, 81 (39.5%) of these patients exhibited lung cavitation, 13 (6.3%) patients afflicted with diabetes mellitus, and 170 (82.9%) isolates belonged to Beijing family. However, the distribution of BDQ resistant isolates showed no significant difference among these characteristics. Of the 86 OFX resistant isolates, 8 isolates were XDR (9.3%, 8/86). Six BDQ resistant isolates (66.7%, 6/9) and two BDQ susceptible isolates (1.0%, 2/196) carried mutations in Rv0678. A total of 4 mutations types were identified in BDQ resistant isolates, including mutation in A152G (50%, 3/6), T56C (16.7%, 1/6), GA492 insertion (16.7%, 1/6), and A274 insertion (16.7%, 1/6). BDQ showed excellent activity against MDR-TB in Chongqing.

Conclusions: BDQ showed excellent activity against MDR-TB in Chongqing. The resistance rate of BDQ was not related to demographic and clinical characteristics. Mutations in Rv0678 gene were the major mechanism to BDQ resistance, with A152G as the most common mutation type. WGS has a good popularize value and application prospect in the rapid detection of BDQ resistance.