Objective:To study the prevalence

phenotypes and genotypes of ESBLs and AmpC-producing 120 nonrepetitive clinical isolates of K.pneumoniae.Methods:The occurrence of phenotype producing ESBLs was screened and determined according to the National Committee for Clinical Laboratory Standards(NCCLS).The phenotypes ofβ-lactamase were studied by isolectric focusing and conjugation methods.The plasmid and genomic DNA extracted from the bacteria were used to determine genotype of theβ-lactamases by PCR with bla

blaTEM

blaSHV and blaAmpC-specific primers.~ts:The study showed that among 120 isolates

theβ-lactamaseproducing strains

ESBLs-producing and AmpC-producing strains were 93(77.5%)

15(12.5%)and 9(7.5%)isolates

respectively. The ESBLs-producing strains were much more frequently found in nosocomial isolates(25.5%)than that in community(3.7%).And all AmpC-producing strains were found in nosocomial isolates.None of them was resistant to imipenam.Furthermore

AmpC-producing strains were found to be more resistant to antibiotics than AmpC negative strains.The encoding genes could be transferred by conjugation and were found in 9 of 18 resistant strains producing both ESBLs and AmpC.Conclusion:A high incidence of ESBLs and AmpC -producing strains existed in K.pneumoniae.Theseβ-lactamase producing strains had been the main pathogens of nosocomial infection. Otherwise

that the gene encoding ESBLs and AmpC could be transferred to susceptible strains by conjugation leading to the resistance spreading abroad.