[Studies on mutation of isoniazid resistant genes in M. tuberculosis].

OBJECTIVE: To understand mutation of isoniazid-resistant genes in M. tuberculosis clinical isolates, and to develop the method for rapid detection of drug resistance. METHOD: Analyzing the katG genes in 30 M. tuberculosis clinical isolates with PCR-SSCP(single stranded conformation polymorphism) and PCR-DS (direct sequencing) techinques. RESULTS: With the reference of M. tuberculosis strain H37 Rv was used as control, all isoniazid-sensitive isolates and 4 isoniazid-resistant isolates displayed ab normal PCR-SSCP and PCR-DS patterns. But of 12 isoniazid-resistant isolates, 4(33.4%) isolates displayed abnormal katG PCR-SSCP pattern, 8 (46.7%) isolates displayed abnormal katG PCR-SSCP pattern, 5(41.7%) isolates were missense mutation at codon 94, 3(25%) isolates were cosense mutation at codon 96. CONCLUSIONS: Resistance to isoniazid in most M. tuberculosis isolates is due to the mutations on katG genes. PCR-SSCP techniques could be used as a method for rapid detection of isoniazid-resistance in M. tuberculosis.