Isolation and Lysogenic Transfection of Verocytotoxigenic Bacteriophage in E.coli

5 strains of verocytotoxigenic (VT) bacteriophage were isolated from E.coli O157 strains, cow feces, chicken feces, sewage and purified by two-layer agar assay. Gene vt2 was amplified by PCR in these phage isolates. The plaques of these phages were 0.5-2mm in diameter and the titre of phages with lucidity plaques against host strain MC1061 was more than 109 PFU/mL. A lysogen with vt2 gene was obtained after transfecting MC1061 by VT2 phage SHФW1 isolated from sewage. The cytopathic effect on Vero cells was produced after inoculating the filtrate from the above lysogen, while no cytopathic effect was appeared inoculating the filtrate from MC1061 cultured in the same condition. All these showed that VT2 phages were common in environment and VT2 virulent factor could transfer horizontally through the lysogenic infection by VT2 phage. VT2 phage is related to the virulence of bacteria.