Primary Exploration On The Role Of FimH Gene In Uropathogenic Escherichia Coli Type1Fimbriae Adhesion

Objective Uropathogenic Escherichia coli (UPEC) is the major pathogenic bacteria to Urinary tract infection (UTI).UPEC injures host through different kinds of virulence factors which fimbriae plays an important role in adhesion and invasion especially the fimbriae Type1. FimH protein located on top of the fimbriae Type1which is coded by fimH gene can adhere to epithelial cells, and the process is the key point of UTI. To clarify on the influence of fimH gene to uropathogenic Escherichia coli (UPEC) Type1fimbriae adhesion function as well as the different gene variation between Type1fimbriae adhesion positive group and negative group, for the development of the related vaccine and Urinary tract infection (UTI) therapy by induced mutation.Methods A total of171UPEC strains(not catheter associated) were collected from the Second Hospital of Tianjin Medical University, Tianjin First Center Hospital, and Tianjin Children’s Hospital during January2012and January2013. The association between fimH gene carrying feature and Type1fimbriae adhesion were carried out by PCR technique and Yeast agglutination test. RT-PCR was used to exterminate gene transcript factor impacting on adhesion. Gene sequencing was applied to compare the variation between the adhesion positive group and negative group.Results Within171UPEC srtains in Tianjin, fimH gene of29strains was negative, and fimH gene of142strains was positive. The carrying rate of fimH gene was83%. Type1fimbriae of98strains was negative, and Type1fimbriae of73strains was positive. The expression rate of Type1fimbriae was57%. All adhesion positive strains carried fimH gene, however, carrying fimH gene was uncertain to express adhesion function. Among44strains with positive fimH gene and negative adhesion RT-PCR revealed that fimH gene did not transcript in8strains (18%). The sequencing results showed from34bp to873bp, there were62SNPs within53polymorphic sites. Amino acid alignment results showed that9SNPs led9amino acid changes, including49th,51st,90th,94th,102nd,128th,187th,190th and219th amino acid sites.94th,102nd and187th amino acid sites mutated frequently, and there was no statistically significant difference between the two groups in the above three sites (χ2=0.11,0.08å'Œ0.45, P>0.05).49th,90th and128th amino acid sites did not mutate frequently, and there was no statistically significant difference between the two groups in the above three sites (χ2=0.21,0.00å'Œ1.47, P>0.05).The sequencing results showed that the difference between two groups in3missense mutations was statistically significance. Gene mutation was easily occurred on the51st amino acid site of the adhesion positive group compared with the negative group (x2=6.64, P=0.010), provided auxiliary method to adhesion detection. In adhesion negative group, mutations on the190th and219th amino acid sites contained6strains and7strains respectively. Nevertheless, the positive group did not occur (χ2=4.69å'Œ5.87, P<0.05), suggesting that the two site mutations would have impact on Type1fimbriae adhesion function. Negative adhesion of other23strains of could not attribuite to single nucleotide polymorphism (SNP)Conclusion Adhesion function of Type1fimbriae could be affected by Mutation and deletion of fimH gene, as well as transcriptional regulation. Three key site mutations that this paper found could affect too. Meanwhile, it could be affected by other genes except fimH gene.