Antibody-direct epifluorescent filter technique and immunomagnetic separation for 10-h screening and 24-h confirmation of Escherichia coli O157:H7 in beef

Abstract

Rapid screening of beef for the presence of Escherichia coli O157:H7 was shown to he feasible using a 10-h enrichment in modified buffered peptone water and the antibody direct epifluorescent filter technique (Ab-DEFT). The Ab-DEFT involved membrane filtration, fluorescent antibody staining and epifluorescence microscopy and was accomplished in less than 1 h. The procedure allowed detection of the pathogen artificially inoculated into beef patties at 0.1 CFU/g. The 10-h nonselective enrichment broth supported rapid growth, which provided sufficient numbers of cells for a positive determination by the Ab-DEFT after fewer than 10 microscope fields were scanned using a 40X objective lens. Immunomagnetic separation rising anti-E. coli O157 Dynabeads® was used to confirm presumptively positive cultures within 24 h. The ease and rapidity of the Ab-DEFT may provide a substantial time and cost savings to the beef industry for screening beef for the presence of E. coli O157:H7.