title: Target site modifications and efflux phenotype in clinical isolates of Streptococcus pneumoniae from Hong Kong with reduced susceptibility to fluoroquinolones.
abstract: Ciprofloxacin-susceptible (n = 7) and -resistant (MIC >or=4 mg/L) (n = 15) clinical isolates of Streptococcus pneumoniae from diverse sources in Hong Kong were studied for target site modifications and efflux phenotype. Reserpine-inhibited efflux of ciprofloxacin and/or levofloxacin was common in both susceptible and non-susceptible isolates. The ParC substitutions K137N and/or S79F or Y were associated with increased ciprofloxacin MICS. The GyrA substitution S81F was only found in isolates with full resistance to ciprofloxacin (MIC >or=16 mg/L) and levofloxacin (MIC >or=8 mg/L). Among clinical isolates of S. pneumoniae, accumulation of target site mutations in strains with an efflux mechanism was associated with increasing MICs of fluoroquinolones.
authors.affiliation: Department of Microbiology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China. plho@hkucc.hku.hk
authors.forename: P L
authors.initials: PL
authors.lastname: Ho
authors.forename: W C
authors.initials: WC
authors.lastname: Yam
authors.forename: T L
authors.initials: TL
authors.lastname: Que
authors.forename: D N
authors.initials: DN
authors.lastname: Tsang
authors.forename: W H
authors.initials: WH
authors.lastname: Seto
authors.forename: T K
authors.initials: TK
authors.lastname: Ng
authors.forename: W S
authors.initials: WS
authors.lastname: Ng
mesh_terms: D019943:Amino Acid Substitution; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D001692:Biological Transport; D004352:Drug Resistance, Microbial / Q000235:genetics / Q000502:physiology; D024841:Fluoroquinolones; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D010641:Phenotype; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D024841:Fluoroquinolones