title: Hypermutability in clinical isolates of Klebsiella pneumoniae is uncommon and is unrelated to ciprofloxacin resistance.
abstract: We investigated hypermutability in Klebsiella pneumoniae and its association with ciprofloxacin resistance and mutations in the quinolone resistance-determining region (QRDR). Sixty-four strains of K. pneumoniae isolated in London, UK, between 1995 and 2002 with widely differing ciprofloxacin minimum inhibitory concentrations (MICs) and known gyrA and parC sequences were tested for mutation frequencies by selection with rifampicin. Only three hypermutable (frequency >or=10(-6)) strains were identified, with ciprofloxacin MICs of 0.25 microg/mL, 8 microg/mL and 64 microg/mL. There was no relationship between hypermutation and the ciprofloxacin MIC or QRDR mutations. Screening selected strains with streptomycin did not reveal any hypermutators, and screening with ciprofloxacin identified only two of the three hypermutators identified by rifampicin. Hypermutation in K. pneumoniae is uncommon and does not contribute to accumulation of QRDR mutations or directly to ciprofloxacin resistance.
authors.affiliation: Department of Infectious Diseases, Division of Immunology, Infection and Inflammatory Diseases, School of Medicine, King's College London, St Thomas' Hospital, London SE1 7EH, UK. sivasampu.aathithan@kcl.ac.uk
authors.forename: S
authors.initials: S
authors.lastname: Aathithan
authors.forename: G L
authors.initials: GL
authors.lastname: French
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000235:genetics* / Q000302:isolation & purification; D008131:London; D008826:Microbial Sensitivity Tests; D009154:Mutation; D012293:Rifampin / Q000494:pharmacology; D013307:Streptomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; D012293:Rifampin; D013307:Streptomycin