Abstract: In order to provide a medication scheme for swine Escherichia coli disease, this experiment identified the isolation of strains by the separation of the bacteria culture, staining microscopy, biochemical experiment, PCR detection and drug susceptibility test methods and so on for diarrheal disease pigs’ parenchymal visera and intestinal contents in large-scale swine farms of Tianjin. The results showed that the isolates strain were gram-negative under microscope, which was short rod. Its biochemical reaction was the same as that of Escherichia coli and the strain was sensitive to cefoperazone and piperacillin and was moderate sensitive to ceftriaxone, cefuroxime, kanamycin and chloramphenicol, but resistant to eight drugs, such as ampicillin, cefazolin and so on. PCR amplified the 16S rRNA gene to obtain the desired target band（1 373 bp）. Homology analysis results showed that the isolation strain was similar to the WTPii241 strain, with the similarity of 99.9%. The isolate strain was confirmed to be Escherichia based on the identification results. These results provide a theoretical basis for the clinical use of diarrhea.

Key words: swine diarrhea, Escherichia coli, separation and identification, drug sensitive test