Antibody-direct epifluorescent filter technique for rapid, direct enumeration of Escherichia coli O157:H7 in beef.
Artificially inoculated Escherichia coli O157:H7 was directly enumerated in ground beef and beef exudate, without enrichment or selection, by the antibody-direct epifluorescent filter technique (Ab-DEFT). The total assay time of the Ab-DEFT was less than 1 h. The beef was homogenized, treated for 15 min with trypsin and Triton X-100, and passed through a 5-microns-pore-size prefilter and then through a 0.2-microns-pore-size black polycarbonate filter. The final filter was stained directly with fluorescein-labeled anti-O157 polyclonal antibody, rinsed, and examined by epifluorescence microscopy. The sensitivity of the Ab-DEFT was compared with that of a standard enrichment culture technique. Both methods reliably determined the presence of the pathogen in beef at 16 CFU/g. The Ab-DEFT was also useful for quantifying the pathogen and monitoring its growth in beef.
Tortorello
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National Center for Food Safety and Technology, U.S. Food and Drug Administration, Summit-Argo, Illinois 60501.
Stewart
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DS
D000818:Animals; D000907:Antibodies, Bacterial; D000918:Antibody Specificity; D002417:Cattle; D015169:Colony Count, Microbial / Q000379:methods* / Q000706:statistics & numerical data; D004926:Escherichia coli / Q000145:classification / Q000276:immunology / Q000302:isolation & purification*; D005069:Evaluation Studies as Topic; D005374:Filtration; D005455:Fluorescent Antibody Technique / Q000706:statistics & numerical data; D008460:Meat / Q000382:microbiology*; D012680:Sensitivity and Specificity
D000907:Antibodies, Bacterial