title: Partial characterisation of the acrAB locus in two Citrobacter freundii clinical isolates.
abstract: We studied the mechanisms of resistance to fluoroquinolones in two Citrobacter freundii strains (1.44 and 1.38) isolated from the same patient and belonging to the same clone by pulsed-field gel electrophoresis. This study allowed partial characterisation of the acrA and acrB genes of this microorganism. As previously reported, the two strains showed the same substitutions in the GyrA and ParC proteins (Thr-83-->Ile and Asp-87-->Tyr in GyrA and Ser-83-->Ile in ParC). However, differences were observed in the amount of ciprofloxacin accumulated, with strain 1.38 showing less accumulation. Expression of genes in both strains was analysed using DNA microarrays for Escherichia coli. Ten genes were overexpressed in strain 1.38 compared with strain 1.44, including genes acrA and acrB. Nucleotide similarity between the partially sequenced acrA and acrB genes of C. freundii and E. coli was 80.7% and 85%, respectively. The acrA and acrB genes of C. freundii are similar to those described in E. coli and their overexpression may play an important role in modulating the final minimum inhibitory concentration of fluoroquinolones in collaboration with mutations in the gyrA and parC genes.
authors.affiliation: Servei de Microbiologia, Centre de Diagnòstic Biomèdic, Hospital Clínic, IDIBAPS, Facultat de Medicina, Universitat de Barcelona, Villarroel 170, 08036 Barcelona, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Sánchez-Céspedes
authors.forename: Jordi
authors.initials: J
authors.lastname: Vila
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016971:Citrobacter freundii / Q000187:drug effects / Q000235:genetics*; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004756:Enterobacteriaceae Infections / Q000382:microbiology*; D005243:Feces / Q000382:microbiology; D005798:Genes, Bacterial / Q000235:genetics*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D000900:Anti-Bacterial Agents; D012333:RNA, Messenger; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase