[Show abstract][Hide abstract] ABSTRACT: Pyrazinamide (PZA), an important first-line drug for anti-tuberculosis treatment, demonstrates potent activity against semi-dormant bacilli in acidic environments. However, the diagnosis of PZA resistance is often impeded by technical difficulties.
To characterise mutations in the pncA and rpsA genes among PZA-resistant and PZA-susceptible clinical Mycobacterium tuberculosis isolates circulating in Kazakhstan. The potential use of genotyping to identify PZA resistance was also investigated.
PZA drug susceptibility testing and pncA and rpsA gene sequencing were performed on 77 clinical M. tuberculosis isolates; mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing was performed on 74 clinical M. tuberculosis isolates.
Of the 77 clinical M. tuberculosis isolates, 41 (53.2%) were phenotypically resistant to PZA, whereas 36 (46.7%) were susceptible; 48 (62.3%) of these isolates were also multidrug-resistant (MDR). Furthermore, 38 (49.3%) clinical isolates showed mutations in the pncA gene and its flanking region; the majority of these isolates (n = 36, 94.7%) were also MDR. Gene sequencing showed that only synonymous substitutions affecting rpsA occurred. MIRU-VNTR typing revealed that 78.4% of isolates were of the Beijing genotype.
Sequencing revealed that mutations in pncA, but not in rpsA, occurred in PZA-resistant M. tuberculosis isolates circulating in the territory of Kazakhstan.
Full-text · Article · Feb 2015 · The International Journal of Tuberculosis and Lung Disease
[Show abstract][Hide abstract] ABSTRACT: Kazakhstan is one of the 14 countries with a high rate of morbidity due to multidrug-resistant tuberculosis (MDR TB) in WHO European region. The aim of our study was to characterize mutations associated with drug resistance to rifampicin and isoniazid in Mycobacterium tuberculosis isolates from Kazakhstan. M. tuberculosis strains were isolated from TB patients in different regions of Kazakhstan. A drug susceptibility test was performed on Lowenstein-Jensen medium using the absolute concentration method. Sequencing analysis was performed of the rpoB rifampicin resistance-determining region and the katG gene, the oxyR-ahpC intergenic region, and the inhA promoter region in 259 MDR M. tuberculosis isolates, in 51 isoniazid-resistant isolates, and in 13 rifampicin-resistant isolates. The mutational analysis revealed that the most frequent mutations associated with rifampicin and isoniazid resistance in M. tuberculosis are the substitutions at codons 531 (82.7%) and 315 (98.4%) in the rpoB and katG genes, respectively. In addition, we have found mutations with lower frequency at codon 526 (8.4%), 533 (1.5%), and 516 (1.1%) in the rpoB gene. In 6.2% of the isolates, no mutations were found in the rpoB gene. The findings of this study provide useful data for a better understanding of the mutation spectrum of isoniazid and rifampicin resistance among strains isolated from patients in Kazakhstan. Our results are also useful for the development of diagnostic tests of MDR M. tuberculosis.