title: Prevalence of katG Ser315 substitution and rpoB mutations in isoniazid-resistant Mycobacterium tuberculosis isolates from Brazil.
abstract: METHODS
  Four hundred and sixty-eight isoniazid (INH) resistant Mycobacterium tuberculosis isolates recovered from a selected Brazilian population.
  
  
  OBJECTIVE
  To check for susceptibility to other chemotherapeutic drugs used in TB treatment, and to ascertain mutations involved in INH and rifampicin (RMP) resistance.
  
  
  METHODS
  Antimicrobial susceptibility to RMP, streptomycin and ethambutol (EMB) was evaluated by the resistance ratio method and pyrazinamide (PZA) by activity assay. Single strand conformation polymorphism (SSCP) and sequence analysis were performed in samples from this panel to confirm mutations in codon 315 of the katG and in a 69-bp region of the rpoB gene.
  
  
  RESULTS
  Combined resistance to INH+RMP, INH+ PZA, INH+EMB, and INH+RMP+PZA was shown in respectively 272 (58.1%), 126 (26.9%), 47 (10%), 116 (24.8%) isolates. No katG mutation was found in 19 (39.6%) of 48 strains tested. Ser315Thr substitution was found in 29 (60.4%). All RMP-resistant strains tested (n = 25) showed rpoB mutations. S531L substitution was found in 15 (60%).
  
  
  CONCLUSIONS
  INH-resistant strains isolated from selected Brazilian populations frequently show resistance to other first-line anti-tuberculosis drugs. rpoB mutation was responsible for RMP resistance in all strains. Among INHr strains, katG mutations were shown in only 60.4%. Genetic approaches targeting the rpoB gene but not the katG gene have a high sensitivity to detect resistance among Brazilian M. tuberculosis strains.
authors.affiliation: Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Campinas, Brazil. hofling@hc.unicamp.br
authors.forename: C C
authors.initials: CC
authors.lastname: Höfling
authors.forename: E M
authors.initials: EM
authors.lastname: Pavan
authors.forename: C M S
authors.initials: CM
authors.lastname: Giampaglia
authors.forename: L
authors.initials: L
authors.lastname: Ferrazoli
authors.forename: D C G
authors.initials: DC
authors.lastname: Aily
authors.forename: D M
authors.initials: DM
authors.lastname: de Albuquerque
authors.forename: M C
authors.initials: MC
authors.lastname: Ramos
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D001938:Brazil; D002374:Catalase / Q000235:genetics; D004252:DNA Mutational Analysis; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004352:Drug Resistance, Microbial; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology*; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000472:pathogenicity; D018807:Polymorphism, Single-Stranded Conformational; D015995:Prevalence; D012293:Rifampin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D018088:Tuberculosis, Multidrug-Resistant
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