Abstract: Objective To investig ate the prevalance of lactamases(bla)gene in extended spectrum lactamases(ESBLs)producing Klebsiella pneumoniae(K.pneumoniae)clinicaliso lates.Methods ESBLs were detected with phenotypic screening and confirm a tory tests based on the Clinical and Labo ratory Standards Institute(CLSI).bla(TEM),bla(SHV)and bla(CTX M)genes were am plified by PCR,and the PCR products were cloned and sequenced to identify the irgeno types.Results The positive rates of bla(TEM),bla(SHV)and bla(CTX M)genes were 23.9%(11/46),28.3%(13/46),and 93.5%(43/46),respectively,in 46 strains of ESBLs producing K.pneumoniae.The strains carrying one,two or three kinds of bla genes were 45.7%(21/46),43.5%(20/46),and 6.5%(3/46),respectively.bla(TEM)genes were TEM 1 and bla(SHV)genes were SHV 11,12,28 in all these strains.bla(CTXM)genes were CTXM 15,24,38 in part of these strains.Conclusion CTXM type is the predominant genotypes in ESBLs producing K.pneum oniae,followed by SHV type,some of these strains carry broad spectrumlactam a ses gene TEM 1 or SHV 11.Monitoring the prevalance of lactam a ses genes in ESBLs producing bacte ria contributes torational use of an tibiotics in clinic.