title: Molecular analysis of isoniazid and rifampin resistance in Mycobacterium tuberculosis isolates recovered from Barcelona.
abstract: We studied the presence of mutations in the whole katG gene and specific regions of the oxyR-ahpC and mabA-inhA regulatory region in 61 Mycobacterium tuberculosis isoniazid-resistant isolates. An 81-bp region of the rpoB gene was also sequenced in 17 rifampin-resistant strains. Alterations in the katG gene were detected in 55% of the isolates. Mutation in codon 315 was the most prevalent (32%). Strains showed a high level of resistance, and most maintained a substantial catalase-peroxidase activity. Three strains with an isoniazid MIC of >or=32 microg/ml lacked catalase-peroxidase activity. Two of them had deletions in the catalytic domain of the KatG protein. One strain with deletion and three strains with mutations in the C-terminal domain showed low-level resistance and conserved the catalase-peroxidase activity. Mutations in the mabA-inhA regulatory region were identified in 32% of the isolates. All had low-level resistance, and the vast majority conserved catalase-peroxidase activity. Seventeen percent of the isoniazid-resistant isolates had no detectable alterations at the studied loci. Resistance to rifampin was associated with mutations in the 81-bp of the rpoB gene in all cases. IS6110 analysis indicated that recent transmission contributed substantially to the emergence of isoniazid- resistant tuberculosis in Barcelona through short transmission chains. A rapid genotypic assay, including the 315-katG codon and the -15 nucleotide of the mabA-inhA regulatory region, may cover 62% of isoniazid- resistant strains in Barcelona. In contrast, the targeting of the 81-bp region of rpoB would detect all our rifampin-resistant isolates.
authors.affiliation: Servei de Microbiología, Hospital de la Santa Creu i Sant Pau, Barcelona. pcoll@hsp.santpau.es
authors.forename: Pere
authors.initials: P
authors.lastname: Coll
authors.forename: Lina Marcela
authors.initials: LM
authors.lastname: Aragón
authors.forename: Fernando
authors.initials: F
authors.lastname: Alcaide
authors.forename: Mateo
authors.initials: M
authors.lastname: Espasa
authors.forename: Montserrat
authors.initials: M
authors.lastname: Garrigó
authors.forename: Julià
authors.initials: J
authors.lastname: González
authors.forename: Jose M
authors.initials: JM
authors.lastname: Manterola
authors.forename: Pilar
authors.initials: P
authors.lastname: Orús
authors.forename: Margarita
authors.initials: M
authors.lastname: Salvadó
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002374:Catalase / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D012293:Rifampin / Q000494:pharmacology*
chemical_list: D000995:Antitubercular Agents; D001426:Bacterial Proteins; D002374:Catalase; C480353:katG protein, Mycobacterium tuberculosis; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D007538:Isoniazid; D012293:Rifampin