Phenotypic and Genotypic Characterization of Fecal Escherichia coli Isolates with Decreased Susceptibility to Fluoroquinolones: Results from a Large Hospital-Based Surveillance Initiative

BackgroundThe prevalence of fecal colonization with Escherichia coli that has reduced susceptibility to fluoroquinolones is unknown. A detailed characterization of such isolates is limited MethodsWe conducted 3 annual fecal surveillance initiatives at 2 hospitals from 2002 to 2004. All E. coli isolates with reduced susceptibility to fluoroquinolones (minimum inhibitory concentration [MIC] to levofloxacin, ⩾0.125 μg/mL) were identified. We characterized gyrA and parC mutations and organic solvent tolerance (OST). Isolates were compared using pulsed-field gel electrophoresis ResultsOf 789 fecal samples, 149 (18.9%) revealed E. coli with reduced susceptibility to fluoroquinolones. Of 149 isolates, 102 (68.5%) had a MIC ⩾8μg/mL, 138 (92.6%) had ⩾1 gyrA mutation, 101 (67.8%) had ⩾1 parC mutation, and 59 (39.6%) demonstrated OST. Isolates with a MIC ⩾8 versus