title: Molecular characterization of the first fluoroquinolone resistant strains of Streptococcus agalactiae isolated in Brazil.
abstract: Three isolates of Streptococcus agalactiae, recovered from residents of the metropolitan area of Rio de Janeiro with significant bacteriuria, were found to be resistant to levofloxacin. Determination of the minimal inhibitory concentration (MIC) confirmed one isolate as intermediate and two as resistant to levofloxacin. No reduction in levofloxacin MIC was observed with reserpine, indicating that resistance was not caused by an efflux mechanism. Typical point mutations were observed in the quinolone resistance determinant region of gyrA and parC. Other point mutations in parC generated novel altered codons: Ser80→Pro in the intermediate resistance isolate, and Gly128→Asp in a resistant isolate. Through molecular modeling, it was possible to observe that these novel substitutions might not play a role in resistance, since these amino acids were not involved in the antibiotic binding site. Pulsed field gel electrophoresis profiles revealed a non-clonal trend among these isolates. This is the first report of genetic characterization of levofloxacin-resistant S. agalactiae strains in Brazil.
authors.affiliation: Instituto Biomedico, Universidade Federal Fluminense, Rua Hernani de Melo 101, Niterói, RJ, Brazil. miprosana@vm.uff.br
authors.forename: Rosana Rocha
authors.initials: RR
authors.lastname: Barros
authors.forename: Fabíola Cristina Oliveira
authors.initials: FC
authors.lastname: Kegele
authors.forename: Geraldo Renato de
authors.initials: GR
authors.lastname: Paula
authors.forename: Monique Araújo de
authors.initials: MA
authors.lastname: Brito
authors.forename: Rafael Silva
authors.initials: RS
authors.lastname: Duarte
mesh_terms: D000293:Adolescent; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001938:Brazil; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017354:Point Mutation; D011247:Pregnancy; D013292:Streptococcus agalactiae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase