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 Mycobacterium tuberculosis 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 atpE gene, encoding the target, or in Rv0678, coding for the repressor of the MmpS5-MmpL5 efflux pump. To better understand the spreading of BDQ resistance in MDR-and XDR-TB, in vitro studies could be a valuable tool. To this aim, in this work an in vitro generation of M. tuberculosis mutants resistant to BDQ was performed starting from two MDR clinical isolates as parental cultures. The two M. tuberculosis MDR clinical isolates were firstly characterized by whole genome sequencing, finding the main mutations responsible for their MDR phenotype. Furthermore, several M. tuberculosis BDQ resistant mutants were isolated by both MDR strains, harboring mutations in both atpE and Rv0678 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.

Genetic variants and their association with phenotypic resistance to bedaquiline in Mycobacterium tuberculosis: a systematic review and individual isolate data analysis

“…By summarising 13 years of data, we generated the most exhaustive catalogue to date: 14 unique variants in atpE , 237 in Rv0678 , 28 in pepQ , and 11 in Rv1979c . Results of our systematic literature review confirmed that variants in the atpE gene result in high level resistance, 31 but the evidence originates predominantly from in vitro and animal experiments, with few documented clinical cases. Our results show that variants in the Rv0678 gene are numerous and scattered throughout the gene, with most of the SNPs, insertions, and deletions occurring in phenotypically susceptible clinical isolates.…”

Heterogeneous Streptomycin Resistance Level Among Mycobacterium tuberculosis Strains From the Same Transmission Cluster

“…Given that the STR resistant isolates from TC1-3 were likely being transmitted in the population, we hypothesized that these isolates had unimpaired fitness. Since in vitro growth capacity is a commonly used surrogate for bacterial fitness (Castro et al, 2020;Degiacomi et al, 2020), we compared the in vitro growth profiles of the M. tuberculosis isolates in TC1-3 to those of a group of susceptible isolates from the same TB cohort (Figure 2A). M. tuberculosis isolates in TC1-3 presented lower times to positivity than the STR susceptible isolates, but similar growth rates and doubling times (Figure 2B).…”

The Iron Chelator Desferrioxamine Increases the Efficacy of Bedaquiline in Primary Human Macrophages Infected with BCG

“…No study to our knowledge has previously shown enhanced bactericidal activity with an iron chelator and a TB antimicrobial in combination. Interestingly, bedaquiline-resistant TB cases are on an upward trajectory [ 28 ]. For example, it was recently discovered that a multi-drug resistant Mtb outbreak in Eswatini is associated with significantly higher resistance to bedaquiline [ 29 ].…”