Abstract: Objective To define the geno typic distribution and combination forms of papG and papA of 45 uro pathogen icE scherichia coli(UPEC)strains isolated in China,and to lay a foundation of further study on pathogenesis,genetic variation,epidemiological analysis as well as immuno the rapy.Methods The papA and papG genes of 45 UPEC stains were typed by the multiplex PCR assay and the genotypicd istribution and combination forms of the two genes were analysed.Results Among the 45 strains,all the strains carried class' geno types of papG(44,97.8%)were found by the multiplex papA PCR assay(F-PCR)to containing one or more of 11 known papA alleles(F-types).Only one stra in(UPEC4030)was negative according to F-PCR assay and by PCR.Hence,it was suspected of harboring novel variant of papA.Of the F PCR positive strains,24(54.55%)had a single F types,13(29.55%)had two types,4(9.09%)and 3(6.82%)had three and four types.F7-2(25.00%),F 11(6.82%)and F16(9.09%)tended to occur a lone.Among the 11 known F types,nine F types occurred at least once in the population in decrea sing order of prevalence as follows:F 10 and F13(27.27%),F7-2 and F11(25.00%),F14(22.27%),F16(20.45%).The combination forms with more than 2 papA geno types were different from those found abroad.The strains containing four F types(F8,F9,F13 and F 14)were found for the first time.Conclusion The results suggested that the papG sequences of UPEC strains isolated in China were highly conserv ative and the papA sequences possessed polymorphisms.The 45 UPEC strains isolated had different papA geno types from those found outside China and their clinical and epidemiological meaning need further study.