Epidemiologic Survey On Escherichia Coli O157 In Chongqing And Three-gorges Reservoir Area

Enterohaemorrhagic Escherichia coli (EHEC) is a very important occasion for food-borne disease in the world. It is associated with a spectrum of illnesses that includes diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome(HUS).Whereas EHEC isolates belong to many different serotypes, O157:H7 is the most common serotype associated with human illnesses.This isolate has caused many outbreaks in the world. In China,E.coli O157:H7 has caused two outbreaks in Jiangsu and Anhui provinces in 1999 and 2000,and expanded to the scope of the Northeast,North China and East China areas. The disease caused by these bacteria has been a serious infectious disease that threat human life and health.So,it has an important significance to investigate the sources, transmit approach and transmit scope of this bacteria and provide the scientific evidence to the prevent and cure the disease.1 .Isolation and identification of Escherichia coli O157 and its phenotypic characteristicsObjective To acquire epidemical data of Escherichia coli O157 isolated from domestic animals in Chongqing and Three-gorges Reservoir Area and make clear the biochemical characteristic and the sensitivity to antibiotics of the isolated bacteria. Methods 1473 rectal fecal samples were collected from six counties.The collected samples were cultured with shaking in mEC+n broth at 37℃ for 6 hours,and then the enriched culture were cultivated on CT-SMAC plates at 37℃ for 18 hours.The suspicious bacteria grown on the plates were identified by serological testing, PCR spreading and microbiochemical reactions. The sensitivity to antibiotics of the isolated bacteria was tested.too.Result 11 strains of Escherichia coli O157 were isolated from 1473 rectal fecal samples and 7 of them are O157:H7s and the rest are O157:H?s.These strains exhibited certain degrees of drug resistance to penicillin,ampicillin,bacitracin, cefuroxime,erythromycin,gentamycin, tetracycline, and so on. Conclusion It was the first complete investigation which found out the sources of E.coli O157 in Chongqing and Three-gorges Reservoir Area and the phenotypic characteristics of the isolates had been studied.2.Detection of virulence and adherence associated genes of Escherichia coli O157 Objective To acquire the data of virulence and adherence associated genes in Escherichia coli O157 . Methods E. coli O157 isolates were examined by polymerase chain reaction (PCR) assay to determine the presence of stx1, stx2,eaeA,ehxA,EspA and Tccp .Result All O157:H7 isolates had eaeA,ehxA,EspA and Tccp genes,but had not stx1 and stx2.All O157:H? isolates had not stx2,eaeA,ehxA,EspA and Tccp genes,and All O157:H? isolates had not stxl except BYY119. Conclusion All O157 isolates isolated in Chongqing and Three-gorges Reservoir Area lack of stx2,so they had a low pathogenesis relatively.