Molecular analysis of rifampin and isoniazid resistance of Mycobacterium tuberculosis clinical isolates in Seville, Spain

In this study we examined the mechanisms of resistance to rifampin (RMP) and isoniazid (lNH) in 352 clinical isolates of Mycobacterium tuberculosis from Sevilla, Spain, using three different molecular methods: 1) PCR-single strand polymorphism analysis; 2) the commercial system Inno-LiPA RTB for RMP resistance; and 3) sequence analysis. Resistance to RMP was found in 21 strains, where the following mutations in the rpoB gene were detected: Ser₅₃₁→ Leu (n =14 strains); His₅₂₆→ Asp (n =3), Asn₅₁₈→ Ser (n =1), Gln₅₁₃→ Leu (n =1) and a nine nucleotide deletion (n =1). Resistance to INH occurred in 29 strains, with mutations observed in: a) kat G gene: Ser₃₁₅→ Thr (n =12), lle₃₀₄→ Val (n =1), and a partial deletion (n =4); b) regulatory region of the inh A gene: nucleotide substitution C209T (n =3). No mutation was found in the ahp C promoter.