Phenotypic and genotypic characterizations of Chinese strains of Escherichia coli producing extended-spectrum beta-lactamases

Twenty-three multi-resistant strains of Escherichia coil were isolated at a single hospital in Beijing, China between January 1997 and May 1998. All i solates produced extended spectrum beta-lactamases (ESBLs) as detected by t he double disk synergy test and the Etest ESBL strip (AB BIODISK Solna Swed en). Additional antimicrobial susceptibility testing showed that most isola tes were resistant to gentamicin, tobramycin, tetracycline, trimethoprim/su lfamethoxazole, ciprofloxacin, and cefepime. All isolates remained suscepti ble to imipenem with MICs of less than or equal to 0.5 mu g/ml. The isolate s each produced several beta-lactamases (range 1-4 enzymes/strain) with pI values ranging from 5.2-8.4. Molecular epidemiologic typing revealed Jolts ribotypes and eight pulsed field gel electrophoresis (PFGE) patterns with s ubgroups among the 23 isolates. Clusters of isolates with the same DNA type were observed as follows (ribotype/PFGE): Wards A (242-5/2, and 242-5/3a), B (242-5/4), and C (880-1/1a). Moreover, similar molecular types were obse rved iir patients from two or more different wards. Further use of isoelect ric focusing results and co-resistance patterns produced evidence of potent ial nosocomial dissemination of strains in only two instances (two identica l strains on one ward and two identical strains on different wards). There were also strong similarities in beta-lactamase pIs and co-resistances amon g many Of the strains throughout tills medical center. These data document the wide genetic diversity among E. coli producing ESBLs, nod a potential f or nosocomial spread of these highly resistant organisms requiring increasi ngly more sophisticated molecular-based techniques and local interventions. (C) 1999 Elsevier Science Inc.