A Study Of Rep-PCR In Source Tracking Of Enterotoxigenic Escherichia Coli And Salmonella Isolated From The Environments Of Cowsheds

Various bacteriosises are so harmful to the development of stock farming. Pathogenic bacteria is one ofthe main factors of environmental pollution of animal houses. Enterotoxigenic escherichia coil (ETEC) andSalmonella are the major pathogenic bacteria from the environments of cow houses, which spread widely andeasy to generate the drug resistance. The Rep-PCR fingerprinting analysis is one microbial source trackingmethod, which has the advantages of high typing rate and discrimination, well reproducibility, easy tointerpret. To provide scientific basis for further control and intervention, Rep-PCR method was used toanalyze the similarity of isolated ETEC strains and Salmonella strains from the the environments samples inthe cow houses. Our findings will provide a theoretical basis for the establishment of management system ofenvironmental monitoring in cow houses.In this study, the976specimens, including ambient air, water, feed, packing of house and feces, werecollected from12cow houses in4farms. The ETEC strains and the Salmonella strains isolated from the976specimens by the methods of isolation, culturing, PCR identification and medicinal sensitivity test. Rep-PCRwas expanded with the support of the primers can obtain Rep-PCR fingerprints. The Rep-PCR technologywas used to amplify the isolated ETEC DNA and Salmonella DNA samples, we can obtain Rep-PCRfingerprints to identify the similarity of isolated ETEC and Salmonella at different sampling points.Meanwhile, medicinal sensitivity test was used to test antimicrobial susceptibility of isolated ETEC strainsand Salmonella strains from the dead cows and diarrheal cows. The Rep-PCR method was used to trace thesource of isolated ETEC strains and Salmonella strains from the dead cows and diarrheal cows.The results showed that153strains of ETEC and42strains of Salmonella isolated from976specimens.The isolating rates were15.7%and4.3%. The ETEC strains and the Salmonella strains were resistant toRifampin, Clindamycin and Amoxicillin. The ETEC strains were sensitive to chloramphenicol, norfloxacin,kanamycin, enoxacin, ofloxacin, the Salmonella strains were sensitive to norfloxacin, Amikacin, gentamicin,kanamycin, spectinomycin, enoxacin, ofloxacin and cefepime.Rep-PCR results showed that the part of ETEC isolated from the air had more than90%similarity withthose isolates isolated from the feces; the ETEC isolated from the water had more than90%similarity withthose isolates isolated from the air, the feces and the packing of house; the ETEC isolated from the feed hadmore than90%similarity with those isolates isolated from the air, the feces and the packing of house; theETEC isolated from the packing of house had more than90%similarity with those isolates isolated from theair and the feces.Rep-PCR results showed that the Salmonella isolated from the air had more than90%similarity withthose isolates isolated from the feces; the Salmonella isolated from the water had more than90%similaritywith those isolates isolated from the air, the feed and the feces; the Salmonella isolated from the feed hadmore than90%similarity with those isolates isolated from the air and packing of house.Three strains of ETEC and one strains of Salmonella isolated from the dead cows and diarrheal cows.The ETEC strains were resistant to Erythrocin, Penicillin, Rifampin, Clindamycin and Amoxicillin. The Salmonella strains were resistant to Acheomycin, Erythrocin, Penicillin, Rifampin, Gentamicin, Clindamycinand Amoxicillin. Rep-PCR results showed that we can not find the source of the ETEC strain. The other twostrains were from the water and the packing of house. The Salmonella strains was from the feed.To sum up, Rep-PCR method has a better discriminant analysis of the strains. The method can be usedas a powful tool to the study of the transmission and souse of ETEC and Salmonella from animal houses totheir environments. Our findings will provide a feasible method for the establishment of traceability systemof environmental bacteria in cow houses.