Epidemiological Study On E.coli O157 From Domestic Animals And Fowl In Chongqing Urban District

Object:To understand the distribution of E.coli O157 in domestic animals and fowl in chongqing urban district, the traits of isolates and associated epidemiological informations. To provide scientific basis for the prevention and control of E.coli O157 infections.Methods:Specimens of animal feces and enviromental samples were collected from stock farms in five districts from June to September in 2001.E.coli O157 isolated from total 570 specimens by IMS were tested for antibiotic susceptibility,plasmid profiles,plasmid restriction endonuclease profiles and pathogenic factors.Results:17 strains of E.coli O157 were isolated,the mean detection rate was 2.98%.14 strains belong to O157:H7,3 strains O157:NM.The bacteria were isolated from cow,chickens,goats and enviroment ,but none from pigs.The corresponding detection rates were 1.65%,1.97%,12.5% respectively.Among them,3 strains were detected fromenviroment.E.coli O157 was not detected from Shapingba and Jiulongpo districts and only isolated from June to Augest.All isolates were of basic biochemistry traits of E.coli,but partial strains couldn't ferment sorbitol,some shew negtive results of Lysine and IND tests.All strains were susceptible to AM/SU,CEC,CRO,AZT,and the resistance to SMX and TX was severe as drug-resistance rate was respectively 88.24%,70.59%.There were about 69% of isolates resisted to no less than two kinds of antibiotics and three of them shew resistance to eight.Four strains could synthesize β-Lactamase which was most likely encoded on a plamid of 3 Kb.All strains harboured plasmids. The plasmid profiles detected in this study were divided into eight types, A to H, which carried 95 and 24Kb plasmids in common. The plasmid profiles and plasmid restriction endonuclease profiles of two strains, one isolated from cow feces and the other sewage near the same farm, were identical to each other, so they might belong to the same clone and have epidemiological relation.Culture suspension of 7 strains could cause rats die,four of which could produce Vero-toxin.Culture broth of the other ten strains also could cause pathological changes in rats and resulted in death.So the isolatedstrains might have some new pathogenic factor.Conclusion:There were two types of E.coli O157 from domestic animals and fowl in chongqing urban district. The toxic factors of the isolated strains were different from the reference strains in China and foreign country. The bacteria excreted by host had already polluted surroundings, especially water-medium, and caused threats to public health. Suggestions for prevention and control were discussed too.