Molecular genetic analysis of Isoniazid-resistant strains of Mycobacterium tuberculosis circulating in the Saratov region

The distribution and mutation spectrum of the katG, inhA, and ahpC genes encoding Isoniazid resistance have been studied in 257 patients with active lung tuberculosis in Saratov oblast. The tests were performed using biological microchips from TB-Biochip MDR pharmacological kits (Russia). The incidence rate of Isoniazid-resistant M. tuberculosis strains was found to be 55.7%. Isoniazid-resistant strains demonstrated a high rate (26.9%) of combined mutations in two and three genes simultaneously and predominance in gene katG Ser315 → Thr1 (91.1%) inducing high resistance to Isoniazid. The sensitivity and specificity of the TB-Biochip MDR test system were 88.2 and 91.3%, respectively. The results of this work show additional measures must be taken to reduce the incidence of Isoniazid-resistant strains.