The katG gene mutations and molecular epidemiological survey in isoniazid resistant and susceptible strains of Mycobacterium tuberculosis

Objective To study katG gene mutations and molecular epidemiological distribution characteristics in isoniazid resistant clinical isolates of Mycobacterium tuberculosis. Methods A total of 123 strains of Mycobacterium tuberculosis were analyzed by PCR-SSCP and DR-based Spoligotyping DNA fingerprinting. Results Point mutations at position 315 were found in the genomes of 60% (27/45)of isoniazid resistant strains. Low level isoniazid resistant strains (1 mg/L) had higher mutation frequency at position 315 than high level isoniazid resistant strains (10 mg/L;χ2=9.31,P0.05). No mutations were identified in the katG gene at position 315 in 53 isoniazid susceptible isolates. 101 of 121 M tuberculosis strains from this survey were determined to be “Beijing Genotype” M tuberculosis strain by DNA fingerprinting analysis, and 18 of 121 strains were scattered in 13 kinds of the other Genotypes.Conclusion These studies provide further evidence supporting the association between katG, gene mutations and INH resistance in Mycobacterium tuberculosis; M tuberculosis strains of Beijing Genotype are prevailing in Beijing district at present.