Analysis of antimicrobial susceptibility and mutations of genes associated with rifampicin and isoniazid resistance in Mycobacteria tuberculosis isolates from 7 patients with cutaneous tuberculosis.

Objective To assess the antimicrobial resistance and resistance-related mutations in rpoB and katG genes in Mycobacteria tuberculosis isolates from patients with cutaneous tuberculosis. Methods Seven strains of Mycobacteria were isolated from lesions or secretions of patients with cutaneous tuberculosis and identified as M. tuberculosis. Proportion method was used to test the susceptibility of M. tuberculosis isolates to rifampicin, isoniazid, streptomycin and ethambutol. PCR and sequencing were performed to analyze the mutations in rpoB and katG genes. Results Of the 7 isolates of M. tuberculosis, 1 was resistant to rifampicin,isoniazid and ethambutol simultaneously, and the other 6 were sensitive to rifampicin, isoniazid, streptomycin and ethambutol. All the 7 isolates were positive for the amplification of rpoB and katG genes by PCR. DNA sequencing revealed two mutations at codon 531 (TCG to TTG) and codon 315 (AGC to ACC) in the multi-drug resistant strain, which were absent in the other 6 strains. Conclusion Multi-drug resistance has emerged in M. tuberculosis isolates from patients with cutaneous tuberculosis, which is likely to be related to improper treatment. Key words: Mycobacteriun tuberculosis;  Drug resistance;  Genes, rpoB;  Genes, katG