RESUMO
OBJECTIVE: To evaluate the relationship between katG gene mutation and isoniazid (INH) resistance and to develop a rapid screening method of point mutation in the katG gene associated with MTB resistance. METHODS: Twenty-four clinical isolates of MTB with 8 INH resigtance isolates and 16 INH-sensitive isolates were analyzed by PCR-RFLP, with the H(37)Rv reference strain as the control. RESULTS: G-->C point mutations were detected in 7 of 8 isoniazid-resistant strains and no gene mutation was shown in 16 isoniazid-sensitive isolates. The sensitivity and specificity were 87.5 % and 100 % respectively. No katG gene sequence deletion was observed in any specimen. CONCLUSION: Our results suggest katG gene mutation is one of the most important mechanisms of INH-resistant TB. PCR-RFLP may be useful in detection of katG gene mutation.