Gene mutations in resistant strains of Mycobacterium tuberculosis isolated from pulmonary tuberculosis patients in Mazandaran and Golestan provinces of Iran - A cross-sectional study

Due to the significant prevalence of tuberculosis (TB) in Mazandaran and Golestan provinces in northern Iran, we aimed to investigate the gene mutations in resistant Mycobacterium tuberculosis isolated from pulmonary TB patients in these provinces of Iran. In this cross-sectional study, sputum of TB suspected patients were collected and cultured in a period of 3 months. The antibiotic-resistant cases identified using the resistance ratio method. Then, the DNAs of the resistant isolates were extracted manually by the CTAB-Proteinase K method and investigated for gene mutations using PCR and sequencing. Among 26 isolated M. tuberculosis, 4 isolates (15.38%) were resistant to antibiotics, while one (3.84%), 2 (7.69%), and one (3.84%) isolates were resistant to rifampin, isoniazid, and multidrug-resistant (MDR), respectively. The MDR isolate had a mutation in codon 315 of the KatG gene resulting in the conversion of serine to threonine, and a mutation in the codon 450 of the rpoB gene, causing the alteration of serine to leucine. In the rifampin-resistant isolate, a mutation occurred at the same locus converting serine to leucine. The low prevalence of antibiotic resistance in this study indicates the appropriate treatment of the patients, however, the single MDR isolate was identified in Mazandaran province.