In vitro Study of Bedaquiline Resistance in Mycobacterium tuberculosis Multi-Drug Resistant Clinical Isolates

Abstract

Tuberculosis (TB) is one of the major causes of death related to antimicrobial resistance worldwide because of the spread of <i>Mycobacterium tuberculosis</i> multi- and extensively drug resistant (multi-drug resistant (MDR) and extensively drug-resistant (XDR), respectively) clinical isolates. To fight MDR and XDR tuberculosis, three new antitubercular drugs, bedaquiline (BDQ), delamanid, and pretomanid were approved for use in clinical setting. Unfortunately, BDQ quickly acquired two main mechanisms of resistance, consisting in mutations in either <i>atpE</i> gene, encoding the target, or in <i>Rv0678</i>, coding for the repressor of the MmpS5-MmpL5 efflux pump. To better understand the spreading of BDQ resistance in MDR- and XDR-TB, <i>in vitro</i> studies could be a valuable tool. To this aim, in this work an <i>in vitro</i> generation of <i>M. tuberculosis</i> mutants resistant to BDQ was performed starting from two MDR clinical isolates as parental cultures. The two <i>M. tuberculosis</i> MDR clinical isolates were firstly characterized by whole genome sequencing, finding the main mutations responsible for their MDR phenotype. Furthermore, several <i>M. tuberculosis</i> BDQ resistant mutants were isolated by both MDR strains, harboring mutations in both <i>atpE</i> and <i>Rv0678</i> genes. These BDQ resistant mutants were further characterized by studying their growth rate that could be related to their spreading in clinical settings. Finally, we also constructed a data sheet including the mutations associated with BDQ resistance that could be useful for the early detection of BDQ-resistance in MDR/XDR patients with the purpose of a better management of antibiotic resistance in clinical settings.