rpoB Mutations Causing Discordant Rifampicin Susceptibility in Mycobacterium tuberculosis: Retrospective Analysis of Prevalence, Phenotypic, Genotypic, and Treatment Outcomes

Abstract

Background Discordant genotypic/phenotypic rifampicin susceptibility testing in Mycobacterium tuberculosis is a significant challenge, yet there are limited data on its prevalence and how best to manage such patients. Whether to treat isolates with rpoB mutations not conferring phenotypic resistance as susceptible or multidrug-resistant tuberculosis (MDR-TB) is unknown. We describe phenotypic and genotypic characteristics of discordant isolates and clinical characteristics and treatment outcomes of affected patients in KwaZulu-Natal, South Africa. Methods We analyzed clinical isolates showing rifampicin resistance on GenoType MTBDR plus while susceptible on 1% agar proportion method. We measured rifampicin minimum inhibitory concentrations (MICs) using Middlebrook 7H10 agar dilution and BACTEC MGIT 960. Sensititre MYCOTB plates were used for drug-susceptibility testing, and rpoB gene sequencing was performed on all isolates. Local MDR-TB program data were reviewed for clinical information and patient outcomes. Results Discordant isolates constituted 4.6% (60) of 1302 rifampicin-resistant cases over the study period. Of these, 62% remained susceptible to isoniazid and 98% remained susceptible to rifabutin. Rifampicin MICs were close to the critical concentration of 1 µg/mL (0.5–2 µg/mL) for 83% of isolates. The most frequent rpoB mutations were Q513P (25.3%), D516V (19.2%), and D516Y (13.3%). Whereas 70% were human immunodeficiency virus infected, the mean CD4 count was 289 cells/mm 3 and 87% were receiving antiretroviral therapy. Standard therapy for MDR-TB was used and 53% achieved successful treatment outcomes. Conclusions Rifampicin-discordant TB is not uncommon and sequencing is required to confirm results. The high susceptibility to rifabutin and isoniazid and poor treatment outcomes with the current regimen suggest a potential utility for rifabutin-based therapy.

Whole Genome Sequencing Results Associated with Minimum Inhibitory Concentrations of 14 Anti-Tuberculosis Drugs among Rifampicin-Resistant Isolates of Mycobacterium Tuberculosis from Iran

“…In addition, there were no strains having mixed mutations within the RRDR. In accordance with the previous studies from different geographical regions [37][38][39], codon 531 of the rpoB gene was the most abundant mutation in this study. Moreover, 85.7% of the RR-MTB strains were found to be resistant to INH (MDR-TB), and testing only the katG gene could detect 83.3% of the strains.…”

Prevalence and Molecular Characteristics Based on Whole Genome Sequencing of Mycobacterium tuberculosis Resistant to Four Anti-Tuberculosis Drugs from Southern Xinjiang, China

“…Identification of resistance-causing SNPs from genomewide sequence is challenging. We chose 7 known resistance genes and regions on the basis of their demonstrated association with drug resistance and according to previous literatures [21][22][23][24] (Table 1). All mutations in these genes and regions were compared with the pan-susceptible reference genome (H37Rv, accession number: NC_000962.2) at the level of SNPs in promoter regions or intergenic regions, amino acids in genes, or insertions and deletions.…”

“…The sequences or regions were chosen on the basis of their demonstrated association with drug resistance according to previous literatures. [21][22][23][24] The results in the present study will be helpful to choose early detection methods of drug resistance (ig, molecular methods) and subsequent initiation of proper therapy of tuberculosis in southern region of Xinjiang, China.…”

Diabetes and multidrug-resistance gene mutation: tuberculosis in Zunyi, Southwest China

“…RIF and INH, as key first-line drugs in anti-TB treatment programs, have always played an important role in the treatment of TB. However, the emergence of MDR-TB may be related to the mutations of the rpoB, katG, and inhA genes of the two drug-related targets (16,17). This study selected TB patients in Zunyi and used polymerase chain reaction (PCR) to detect mycobacterial DNA and RNA (18) for the purpose of investigating the correlation between TB and diabetes mellitus with tuberculosis (DM-TB) in Zunyi.…”