Identification Of Calf Diarrhea In Some Areas Of Beijing And Tianjin And Drug Resistance Of E.Coli Isolated

Most E.coli diarrheal disease are caused by enterotoxigenic Escherichia coli(ETEC),which can cause newborn calves gastrointestinal diseases, dehydration and death. With the popularity of captivity, the spread are rapid when the diseases occur. E. coli is extremely difficult to purify, such as secondary infection lead to greater losses.Currently, we use the antibiotics for the treatment of clinical colibacillosis.The disease can propagate through a variety of ways, and give human food safety and public health greater threat. This test include pathogenic bacteria isolation and identification, antimicrobial susceptibility testing in vitro, resistant genes detection of Beijing, Tianjin and parts of cattle suspected calf diarrheal disease, these can provide an significant effect for the drug selection, prevention, control of calf diarrheal disease. 1.E. coli of pathogens isolated and identifiedDiarrhea from Beijing, Tianjin and parts of four calves cattle farm fresh anus stool samples for bacterial isolation, which identified by physical and chemical identification, bacterial antigen identification, mouse pathogenicity tests, molecular biology.32 isolates of E. coli were isolated including Tianjin(17), Beijing(15), respectively. 2. Drug susceptibility testsWe selected 21 kinds of veterinary antibiotics against pathogenic strains in vitro by Kirby-Bauer paper disc method.The results showed that the norfloxacin resistance rates of pathogenic strains of Tianjin, Beijing area were 100% and 86.67%.Two regions in the levofloxacin resistance phenotypes difference between the maximum reached 87.44%. E. coli calves are all multi-drug resistant in Tianjin, the highest is 16, and the largest proportion is 14.only one strain in Beijing has the one drug resistance, the largest proportion is 13. 3.portions resistance Gene in was amplified by PCRWe detected the resistant genes of β-lactams, aminoglycosides, tetracyclines, chloramphenicol, sulfonamides by PCR assay.We tested the blaTEM, blaCTX gene of β-lactams, the positive rate was 62.5%, 59.38% respectively; aadA, Aph(3’) gene of aminoglycosides, the positive rate was 84.38%, 68.71% respectively; tet(B) gene of tetracycline, the positive rate was 50%; floR, clma gene of chloramphenicol, the positive rate was 65.63% and 75%, respectively; Sul2 gene of sulfa, the positive rate was 65.63%; ParC gene of quinolones, the positive rate was 50%. The amplification product of GyrA, GyrB drug resistance gene of Quinolones compared with the known sequence of positive resistance-determining region after biotechnology company sequencing,the mutation rate was 65.51%, 59.26% respectively.We isolated E. coli and detected resistant genes of Tianjin, Beijing and parts of cattle farm calf of diarrhea by simple physicochemical methods, biology approach and susceptibility tests.This test provides the prevalence of E. coli and drug resistance, which give scientific experimental basis for clinical calf of E. coli diarrhea disease and rational drug use.