EVALUATION OF INHA GENE AND CATALASE-PEROXIDASE GENE AMONG ISONIAZID-SENSITIVE AND RESISTANT MYCOBACTERIUM-TUBERCULOSIS ISOLATES

The katG gene and the inhA gene of 30 INH-resistant (INH-R) and 28 INH -sensitive (INH-S) isolates of M. tuberculosis from Haiti and Maryland were analysed by PCR to establish the presence and frequency of two p ostulated mechanisms of INH-resistance, total katG gene deletion and i nhA Ser(94) to Ala(94) amino acid substitution. Only two of 30 INH-R i solates (3%) appear to have total katG gene deletions. All 28 INH-S is olates (100%) produced a PCR product at both the 5' and the 3' ends of the katG gene. Gene deletion of katG is a rare mechanism of INH resis tance. Allele specific oligonucleotide hybridisation analysis of the i nhA PCR products from the same 58 isolates revealed no mutation at ami no acid 94 or directly surrounding it. Other inhA gene mutations may b e responsible for INH resistance in M. tuberculosis. Diagnostic strate gies using katG gene deletion or inhA Ser(94) mutations would fail to detect almost all INH-R isolates. (C) 1996 Academic Press Limited