Abstract: ObjectiveTo understand the characteristics of the resi/stance of Klebsiella pneumoniae and Escherichia coli producing extended spectrum B-lactamase(ESBLs)and to prevent a nosocomial outbreak of organisms producing ESBLs.MethodsUsing double-disk cooperative test to corroborate K.Pneumoniae and E.Coli measuring up to the screen standar destablished by National Committee for Clinical Laboratory Standards(NCCLS).ResultsTwenty nine strains of all 264 isolates(82 strains of K.Pneumoniae and 182 strains of E.Coli)produced ESBLs,and the positive rate was 11.0%.Among them,the positive rate of K.Pneumoniae was 15.9% (13/82)and that of E.Coli was 8.8% (16/182).Strains producing ESBLs not only had different degree resistance to aminoglycosides,quinolones,sulfa and tetracycline, but also the resistant rate of strains producing ESBLs was obviously higher than that of non-producing ESBLs strains.There was widespread nosocomial dissemination of organisms producing ESBLs which were isolated in various specimen from clinic and 12 wards.ConclusionBacteria producing ESBLs was multiple resistant or ganisms and drug resistant plasmid could spread among bacteria causing regional outbreak and prevalence.