Molecular characteristics and in vitro susceptibility to bedaquiline of Mycobacterium tuberculosis isolates circulating in Shaanxi, China

Abstract

The aim of this study was to investigate the molecular characteristics and in vitro susceptibility to bedaquiline of Mycobacterium tuberculosis (MTB) isolates from Shaanxi, China. Methods: The minimum inhibitory concentration (MIC) of bedaquiline was determined using the microplate alamarBlue assay for 518 MTB isolates from Shaanxi. Isolates with MIC values of bedaquiline !0.12 mg/mL were sequenced for the atpE, Rv0678, and pepQ genes. Drug susceptibility testing and spoligotyping were also conducted for all strains. Results: Ten (1.93%) bedaquiline-resistant strains were isolated from 518 tuberculosis patients. The resistance rate of bedaquiline was not correlated to sex, age, treatment history, region, or genotype. Five bedaquiline-resistant isolates and one bedaquiline-susceptible isolate were found to carry Rv0678 mutations; six mutation types were identified, including G5T, A263G, C185T, G19deletion, C265T, and T323C. No mutations within the atpE and pepQ genes were observed. Conclusions: Bedaquiline showed strong in vitro antibacterial activity against MTB isolates, and the Rv0678 gene serves as the major mechanism contributing to bedaquiline resistance among MTB isolates from Shaanxi, China. Two novel mutation types (C265 T and T323 C) of the Rv0678 gene were associated with resistance to bedaquiline. Furthermore, in addition to the current three resistance-associated genes (atpE, Rv0678, and pepQ), other mechanisms of resistance to bedaquiline may exist that need further study.

Primary Bedaquiline Resistance Among Cases of Drug-Resistant Tuberculosis in Taiwan

“…In this retrospective population-based study, the rate of BDQ resistance (MIC ≥ 0.25 μg/ml) among DR-TB cases without BDQ and CFZ exposure was found to be 3.1% (28/898) in Taiwan, whereas other studies found values of 1.0% in France (Veziris et al, 2017), 1.3% in Russia (Peretokina et al, 2020), 2.2-3.9% in China (Pang et al, 2017;Liu et al, 2020;Yang et al, 2020), and 2.3% in a multicountry population (Diacon et al, 2014;Pym et al, 2016;Villellas et al, 2017). Furthermore, we identified 77.3% (17/22) of MGIT-BDQ-resistant isolates harboring Rv0678 mutations (Supplementary Table S2), which might not be associated with CFZ cross-resistance (Xu et al, 2017;Ghodousi et al, 2019;Beckert et al, 2020), whereas the other studies found corresponding values of 50.0-66.7% in China (Pang et al, 2017;Yang et al, 2020), 66.7% in Australia (Martinez et al, 2018), 71.4% in Germany (Andres et al, 2020), 75.0% in France (Veziris et al, 2017), 100% in South Africa (Nimmo et al, 2020b), 100% in Russia (Zimenkov et al, 2017;Peretokina et al, 2020), and 100% in a multicountry population (Villellas et al, 2017). BDQ resistance might naturally occurred or during treatment with other anti-TB drugs (Yang et al, 2020) or previous use of antifungal drugs (Milano et al, 2009;Hartkoorn et al, 2014).…”

“…Furthermore, we identified 77.3% (17/22) of MGIT-BDQ-resistant isolates harboring Rv0678 mutations (Supplementary Table S2), which might not be associated with CFZ cross-resistance (Xu et al, 2017;Ghodousi et al, 2019;Beckert et al, 2020), whereas the other studies found corresponding values of 50.0-66.7% in China (Pang et al, 2017;Yang et al, 2020), 66.7% in Australia (Martinez et al, 2018), 71.4% in Germany (Andres et al, 2020), 75.0% in France (Veziris et al, 2017), 100% in South Africa (Nimmo et al, 2020b), 100% in Russia (Zimenkov et al, 2017;Peretokina et al, 2020), and 100% in a multicountry population (Villellas et al, 2017). BDQ resistance might naturally occurred or during treatment with other anti-TB drugs (Yang et al, 2020) or previous use of antifungal drugs (Milano et al, 2009;Hartkoorn et al, 2014). In Taiwan, the 4% prevalence rate of azole-resistant Aspergillus fumigatus clinical isolates mainly emerged from the environment and during antifungal treatment (Wu et al, 2020), and its influence on BDQ resistance remains elusive.…”

“…Because most Rv0678 mutations are associated with low-level BDQ resistance (Veziris et al, 2017;Villellas et al, 2017;Xu et al, 2017;Zimenkov et al, 2017;Battaglia et al, 2020;Peretokina et al, 2020;Yang et al, 2020), scarce studies have investigated their impact on treatment outcomes. A study using a mice model showed that BDQ still exhibits bactericidal activity against isolates with Rv0678 mutations and activity lower than that found in the absence of Rv0678 mutations (Andries et al, 2014).…”

“…Of the 28 isolates with BDQ MIC ≥ 0.25 μg/ml, 2.5% (5/202), 3.3% (20/608), 4.1% (3/74), and 0.0% (0/14) cases were classified as RR-TB, MDR-TB, Pre-XDR-TB, and XDR-TB, respectively (Table 2). However, a study conducted in China, the highest BDQ resistance was found in XDR-TB (16.7%), followed by MDR-TB (5.6%) and Pre-XDR-TB (4.2%; Yang et al, 2020).…”

Bedaquiline Adherence Measured by Electronic Dose Monitoring Predicts Clinical Outcomes in the Treatment of Patients With Multidrug-Resistant Tuberculosis and HIV/AIDS

“…19 Phenotypic bedaquiline susceptibility testing found that baseline isolates had MICs at the ecological cutoff for resistance, whereas emergent bedaquiline RAVs all had MICs exceeding the threshold for phenotypic drug resistance. 20 There was no statistically significant association between low bedaquiline adherence and bedaquiline RAVs, given the small patient numbers. However, 2 patients with 100% bedaquiline adherence achieved good outcomes despite bedaquiline RAVs, whereas 5 patients with bedaquiline RAVs and suboptimal adherence all experienced unsuccessful treatment outcomes.…”