REPEATABILITY OF THE PETRIFILM(TM) HEC TEST AND AGREEMENT WITH A HYDROPHOBIC GRID MEMBRANE FILTRATION METHOD FOR THE ENUMERATION OF ESCHERICHIA-COLI O157-H7 ON BEEF CARCASSES

The Petrifilm(TM) HEC test (3M Canada Inc., London, Ontario), a quanti tative microbiological test for Escherichia coli O157:H7, was evaluate d for its performance as a beef-carcass monitoring test. Test repeatab ility and agreement with an E. coli O157:H7 detection method using a h ydrophobic grid membrane filter (HGMF) overlaid onto cefixime-tellurit e-sorbitol MacConkey agar (CT-SMAC) followed by a latex agglutination test for the O157 antigen were determined by using pure cultures of E. coli O157:H7, beef samples experimentally contaminated with bovine fe ces containing E. coli O157:H7, and naturally contaminated beef carcas ses of unknown E. coli O157:H7 status from a local abattoir, The Petri film(TM) HEC test showed excellent repeatability and excellent agreeme nt with the HGMF-CT-SMAC method when test samples were obtained from p ure cultures and experimentally contaminated meat. All 125 naturally c ontaminated beef carcasses surveyed were negative for E. coli O157:H7 with both microbial methods. The Petrifilm(TM) HEC test, however, demo nstrated a significantly lower proportion of cross-reactive organisms (false-positive reactions) than the HGMF-CT-SMAC method. Given the per formance of this test coupled with its ease of use acid compact size, it shows considerable promise for carcass testing where abattoir labor atory facilities are limited and as a substitute for more complex labo ratory testing methods used in established laboratories.