Comparison of vero cell assay, polymerase chain reaction and an enzyme immunoassay for identification of verocytotoxin-producing Escherichia coli O157 : H7

This study evaluated three different analytical methods for identification of Verocytotoxin- producing E. coli O157 :H7 (VTEC) strains. A total of 34 E. coli O157 :H7 strains isolated from bovine faeces and bovine carcasses w ere comparatively tested with Vero cell assay (VCA), PCR and the sandwich E LISA "RIDASCREEN(R) Verotoxin" test. The VCA, performed without a neutraliz ation assay, gave a false positive result because a VCA-positive E. coli O1 57 :H7 strain did not possess the VT-coding genes when tested with PCR. The lack of specificity of the VCA could be avoided by testing for neutralizat ion of cytotoxicity. The commercial ELISA system was as sensitive and speci fic as PCR, with the advantages of being a more rapid and easier procedure which could be employed in all first level diagnostic laboratories.