Characterization of rrs and rpsL Mutations in Aminoglycoside-Resistant Mycobacterium tuberculosis Strains Isolated from Clinical Specimens in the West of Iran

Abstract

Background: The medical significance of drug resistance in Mycobacterium tuberculosis, particularly the multi-drug-resistant strains, has a significant impact on the challenge of treating the disease and controlling its prevalence. Objectives: The objective of this study was to determine the frequency of rrs and rpsL mutations in aminoglycoside-resistant Mycobacterium tuberculosis strains isolated from clinical specimens in western Iran. Methods: This descriptive cross-sectional study was conducted on positive sputum specimens obtained from 40 pulmonary disease patients referred to the Kermanshah Lung Disease Center. The sputum specimens were cultured on the Löwenstein–Jensen medium. Specimens were assessed for the presence of genes resistant and susceptible to aminoglycosides using gene expression methods. DNA extraction was performed using the G-spin kit, and the Polymerase Chain Reaction (PCR) method and hybridization technique were carried out using the AID kit. Results: Out of the 40 sputum samples, five (12.5%) were resistant to kanamycin/amikacin, and 12 (30%) showed resistance to streptomycin. Five mutation sites were identified in the codon 1400 of the rrs gene, which were associated with amikacin/kanamycin resistance. Additionally, nine other samples (22.5%) exhibited mutations in the Streptomycin-resistant rpsL A43G gene. Three samples (7.5%) showed mutations in the rrs C526T gene, conferring resistance to streptomycin. Conclusions: Our investigation revealed a significant frequency of resistance to drugs used as second-line medications. It must be noted that treating patients can be challenging when the frequency of multi-drug-resistant bacteria is high.