In the regions where bedaquiline (BDQ) is introduced into the regimen, analysis of MIC and screening for preexisting resistance mutations could be crucial. The high prevalence of isolates with high BDQ MICs without prior exposure to BDQ was worrisome. It was also concluded that efflux pumps play a pivotal role in intrinsic BDQ resistance; therefore, the potential of verapamil as an adjunctive therapy to combat BDQ resistance should be investigated.
Background
In order to shorten the course of treatment and its effectiveness, it is essential to gain an in-depth insight into the drug resistance mechanisms of
Mycobacterium tuberculosis
(
M. tuberculosis
).
Methods
In this study, we evaluated the contribution of 26 drug efflux pumps plus target gene mutations to the drug resistance levels in multi-drug resistant (MDR)/pre-extensively drug-resistant (pre-XDR)/extensively drug-resistant (XDR) and mono-drug resistant clinical isolates of
M. tuberculosis
. The panels of 25
M. tuberculosis
clinical strains were characterized for drug resistance-associated mutations with whole-genome sequencing and antibiotic profiles in the presence and absence of efflux inhibitor verapamil (VP).
Results
Different MICs were observed for the same target gene mutations. Out of the 16 MDR/pre-XDR/XDR isolates, 6 (37.5%) and 3 (18.8%) isolates demonstrated a significant decrease in rifampicin (RIF) MIC and isoniazid (INH) MIC due to the VP exposure (64 μg/mL), respectively. Susceptibility to RIF was fully restored in two isolates after VP exposure. Moreover, the efflux pump genes of
Rv2938, Rv2936, Rv1145, Rv1146, Rv933, Rv1250, Rv876
,
Rv2333, Rv2459, Rv849,
and
Rv1819
were overexpressed in the presence of anti-TB drugs, showing the contribution of these efflux pumps to the overall resistance phenotype.
Conclusions
Our results clearly showed that efflux systems, besides spontaneous mutations, play a role in the development of INH/RIF resistance. In addition, although VP was effective in reducing the expression of some efflux pumps, it was not very successful at the phenotypic level.
Electronic supplementary material
The online version of this article (10.1186/s13756-019-0516-4) contains supplementary material, which is available to authorized users.
Background
Mycobacterium tuberculosis possesses five resuscitation-promoting factors, Rpf A to E, which are required for the resuscitation of dormancy in mycobacteria. This study explores the transcriptional profile of all five rpfs of M. tuberculosis, in response to sub-MIC concentration of rifampin, in multidrug and mono-rifampin resistant clinical isolates.MethodsThirteen multidrug and two rifampin mono resistant clinical isolates were analyzed. Drug susceptibility testing and determination of MIC were performed. The relative expression of rpfs was measured, by real-time quantitative PCR.ResultsA significant upregulation of relative expression (p < 0.05) was observed, as follows: 7/15(46.66%); 5/15(33.33%); 9/15(60%); 10/15(66.66%) and 9/15(60%) in rpfA, rpfB, rpfC, rpfD and rpfE, respectively.ConclusionOur results showed that the rpfs could be overexpressed in some extent in the presence of sub-MIC concentration of rifampin in multidrug and mono drug resistant M. tuberculosis. These results highlight the potential risk of sub-MIC rifampin concentrations, as a risk factor for tuberculosis reactivation.
Introduction: Despite the moderate incidence of tuberculosis (TB) in many parts of Iran, Golestan province had a permanently higher TB incidence rate than the national average. Moreover, Golestan province receives immigrants, mainly from TB-endemic areas of Iran and neighbor countries. Here, we aimed to characterize the circulating Mycobacterium tuberculosis complex (MTBC) isolates in terms of the spoligotype and drug resistance patterns, across Golestan province. Materials and Methods: A set of 166 MTBC isolates was collected during July 2014 to July 2015 and subjected to drug susceptibility testing for firstand second-line anti-TB drugs and spoligotyping. Results: Of 166 MTBC isolates, 139 (83.7%) isolates were assigned to 28 spoligotype international types (SITs). The most frequent SITs were SIT127/Ural-2 (n=25, 15.1%), followed by SIT1/Beijing (n=21, 12.7%) and SIT3427/Ural-2 (n=18, 10.8%). The set of 18 isolates (10.8%) showed resistance to at least one drug, which mainly belonged to SIT1/ Beijing (n=7, 38.9%), orphan patterns (n=4, 22.2%) and SIT357/CAS1-Delhi (n=3, 16.7%). In addition, four isolates (2.4%) were resistant to pyrazinamide. The analysis of mutation corresponded to resistance to rifampin and isoniazid showed that two isolates had Ser531Leu substitution in rpoB, four isolates had Ser315Thr substitution in katG and one isolate had [C (−15)T] in inhA locus. Conclusion: High diversity in spoligotypes of the MTBC isolates and lack of dominant genotype might be due to residence of immigrants in this region and consequent reactivation of latent infection. In addition, due to the presence of extensively drug-resistant (XDR) isolates in Golestan province, it is important to conduct future studies to determine transmission pattern of drug-resistant isolates in this region.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.