Abstract:

Objective To explore the minimal inhibitory concentration (MIC) of clinical isolates of Mycobacterium tuberculosis (MTB) to bedaquiline (Bdq) by drug sensitivity test, and to analyze the mechanism of drug resistance of MTB to Bdq at the gene level. Methods MTB strains were isolated from 189 pulmonary tuberculosis patients from the cooperative Hospital of NDIP (New Drug Introduction Protection) project. Among them, 130 patients only provided the baseline (within one week before taking the first dose of Bdq) positive strains, and the other 59 also provided the positive strains collected at 2, 4, 8, 12, 16, 20 and 24 weeks after being treated with Bdq. CMP1BDQ 96 well drug sensitive microplate was used to detect the drug resistance of baseline MTB isolates to Bdq and other 11 kinds of anti-tuberculosis drugs, and the drug resistance of MTB clinical isolates to Bdq in different periods after being treated with Bdq regimen. MTB strains resistant to Bdq were screened and sequences of four genes, Rv0678, atpE, pepQ and Rv1979c, were detected. Results MIC values of 86.2% (163/189) of the baseline MTB isolates were below 0.06 μg/ml, MIC₅₀ and MIC₉₀ were 0.03 μg/ml and 0.12 μg/ml, respectively; the primary resistance rate of baseline MTB isolates to Bdq was 2.1% (4/189); the acquired resistance rate of patients to Bdq during the treatment was 1.6% (3/189). Rv0678 mutation was detected in all of the 4 MTB isolates from patients with primary resistance to Bdq, but no atpE, pepQ, or Rv1979c mutations were detected; Rv0678 mutation was detected in MTB isolates from 3 patients with acquired resistance to Bdq, and Rv1979c was detected in 1 case, pepQ or atpE mutations were not detected; of the 3 patients with reduced sensitivity to Bdq, 2 of the MTB isolates were detected with Rv0678 mutation, 1 was detected with Rv1979c mutation, and atpE or pepQ mutations were not detected. Conclusion At present, the drug resistance rate of clinical isolates of MTB to Bdq is low, and drug resistance mutations all occur in known genes, no new drug resistance-related genes have been found.

Key words: Mycobacterium tuberculosis, Microbial sensitivity tests, Drug resistance, Genes, bedaquiline