BioProject

In 2021, an estimated 11 million people contracted tuberculosis (TB) whilst 1. More...

In 2021, an estimated 11 million people contracted tuberculosis (TB) whilst 1.5 million died of the disease. Of those infected, around the 7 million were treated with the 6 month long standard combined drug regimen. While this regimen is reported to have an 85% success rate, the remaining 15 % of patients (approximately 1.6 million people) require further, extended drug treatment. Many of these relapsed TB cases are attributed to the presence of an antibiotic-refractory, phenotypically drug tolerant subpopulation termed persisters. In this study, genes affecting the frequency of these persisters in Mtb were identified using a whole genome screen of a transposon mutant library exposed to the anti-mycobacterial antibiotics rifampicin (RIF) and streptomycin (STM) under conditions that select for phenotypic drug-tolerant persisters. In both the RIF and STM treatment Low persister mutants (lip) that survive less well under antibiotic treatment, and High persister mutants (hip) that survive better under antibiotic treatment were identified. Many of the lip mutations were in genes associated with changes in cell membrane integrity and permeability. With RIF these genes included cpsA/lytR/Psr genes that are involved in arabinogalactan assembly, and several other genes associated with the cell envelope. In contrast, the STM treatment identified a predominance of toxin/antitoxin genes. High persister mutants, hip mutants, included the genes prpC, prpD and prpR of the methyl citrate cycle, and ceoB and the adjacent gene Rv2690c of the K+ uptake trkA-C system for RIF. With STM only the resistance gene, gidB, and the poorly characterised, anion-transport genes Rv3679c and Rv3680c, were identified. Persister are often assumed to be tolerant to multiple antibiotics so perhaps surprisingly, few of the genes identified were common to both treatments. Knockouts were generated for two genes identified under RIF selection, a hip mutant, prpD KO (Rv1130) and a lip mutant fadE5 KO (Rv0244c), and their predicted persister phenotypes confirmed. Overall, these findings indicate that the mechanism behind mycobacterial persisters are drug-specific and highly coordinated. These results may lead to the identification of novel antibiotic-specific treatments to target persisters, and so increase treatment efficacy, reduce treatment length and curtail this global health emergency. Less...