Methods : Nineteen Escherichia coli urinary tract infection pathogens exhibiting high-level resistance to fluoroquinolones were characterized in this study. Alterations in outer membrane proteins (OMPs) and lipopolysaccharide (LPS) were analysed by PAGE. Changes to the quinolone resistance-determining regions (QRDRs) of GyrA and ParC were determined by PCR and DNA sequencing. The presence of the qnrA gene was determined by PCR amplification. Ciprofloxacin uptake was determined spectrophoto- metrically using the quinolone accumulation assay