Detection of extended-spectrum beta-lactamase-producing, multidrug-resistant environmental isolates of Escherichia coli that bind to human bladder cells.

Compared to the number of studies examining extended-spectrum beta-lactamase (ESBL)-producing clinical isolates, environmental ESBL-producers have not been studied extensively. To investigate environmental ESBL-producing Escherichia coli, 22 cephalothin-resistant E. coli were isolated from Han River in Seoul, Korea. These isolates were resistant to ampicillin, cephalothin, and gentamicin, and 14 isolates among these were resistant to norfloxacin. All of these isolates produce AmpC and CMY, OXA, or TEM as determined by isoelectric point focusing (IEF) gel electrophoresis and PCR. One isolate (57-214) producing AmpC and OXA was resistant to all antibiotics (ampicillin, cephalothin, norfloxacin, gentamicin, cefotaxime, ceftazidime) tested in this study. Six isolates, including isolate 57-214, could adhere to T24 human bladder cells, and these isolates were not related to each other as shown with random amplified polymorphic DNA (RAPD). Results showed that environmental ESBL-producing E. coli is able to colonize in bladder cells and directly cause antibiotic-resistant urinary tract infection.