Mutations in the pncA and rpsA genes among 77 Mycobacterium tuberculosis isolates in Kazakhstan

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.