The Horizontal Transfer Of Virulence Factors In Pathogenic Escherichia Coli Isolated From Diseased Pigs And It’s Invasiveness To HEp-2Cells

Disease caused by Pathogenic Echerichia coli is a serious threat to human and animal health. It is always bring economic losses that the outbreak and prevalence of disease casued by E.coli in the livestock industry, such as the Edema Disease of Swine, yellow and white scour of piglets. The incidence rate and mortality rate are all very high. Especially the Edema Disease, its death rate can get90%.Today, there are many pathogenic E.coli that can cause disease both in human and animal. It makes the prevention and treatment of Colibacillosis more difficult for the multi-drug resistance strains become common in clinical. So the research of virulence factor and resistance is hot and difficult.To investigate the role of conjugative plasmid in the spread of virulence and resistance genes, and the diversification of invasiveness to Hep-2cells and antibiotic resistance among the Pathogenic Echerichia coli,52of Pathogenic E.coli strains isolated from diseased pigs in farms surrounding Harbin were used to experiment. The pathogenicity of E.coli was detemined with mice challenge test in vivo. All transconjugants were selected by plasmid conjugation experiment, and compared the resistance, invasiveness and virulence genes with the donor strains. An in vitro model system for bacterial invasion of Hep-2cells was used to compare the invasiveness of donor strains and its corresponding transconjugants. All transconjugants and donor strains were examined for antimicrobial susceptibility to12antimicrobials according to the K-B (Kibry-baue) standard recommended by DLSI (Clinical and Laboratory Standards institute), and tested the virulence genes (VGs) by PCR technique. Finally, the transmission electron microscopy (TEM) was applied to observe the damage of Hep-2cells caused by donor strains and transconjugants.A total of30(57.7%) transconjugants strains were conjugated successfully in this experiment. All the transconjugants showed multiple antimicrobial-resistant to the12antimicrobials which revealed that the capability of transconjugants to catch exogenous genes was strange. The capability of invasion in Hep-2cell for transconjugants strains also changed mostly, especilly the virulence strengthen strains possess a high proportion of43.3%(13/30). Analysis the result of virulence genes detected in donor strains and transconjugants, it also found that pathogenicity island genes(PAIs) of Pathogenic Echerichia coli play an important role in virulence expression for PAIs-negative transconjugants strains has a lower invasiveness compared with its conresponding donor strains. These results suggest conjugative plasmid play an important role in the spread of E. coli virulence factors.In this study, we analysis the variation of virulence and resistance for E.coli after the plasmid-mediated virulence genes and resistant genes horizontal transmission, and even the horizontal transmission can cause the virulence and resistance strength, so it has became one of the effective ways for us to control the virulence and resistance of E.coli that strengthen the research and monitor of Pathogenic Escherichia coli from pigs carried the conjugative plasmid to widespread horizontal transfer of virulence and resistant genes.