Dipstick immunoassay to detect enterohemorrhagic Escherichia coli O157:H7 in retail ground beef.
A sensitive and easy-to-perform dipstick immunoassay to detect Escherichia coli O157:H7 in retail ground beef was developed by using a sandwich-type assay (with a polyclonal antibody to E. coli O157 as the capture antibody and a monoclonal antibody to E. coli O157:H7 as the detection antibody) on a hydrophobic polyvinylidine difluoride-based membrane. E. coli O157:H7 in ground beef could be detected within 16 h, including incubation for 12 h in enrichment broth and the immunoassay, which takes 4 h. Pure culture cell suspensions of 10(5) or 10(6) E. coli O157:H7 organisms per ml produced intense color reactions in the immunoassay, whereas faint but detectable reactions occurred with 10(3) CFU/ml. The sensitivity of the combined enrichment-immunoassay procedure as determined by using ground beef inoculated with E. coli O157:H7 was 0.1 to 1.3 cells per g, with a false-positive rate of 2.0%. A survey of retail ground beef using this procedure revealed that 1 of 76 samples was contaminated by E. coli O157:H7.
Kim
M S
MS
Department of Food Microbiology and Toxicology, University of Wisconsin, Madison 53706.
Doyle
M P
MP
D000818:Animals; D002417:Cattle; D004926:Escherichia coli / Q000302:isolation & purification*; D005516:Food Microbiology; D006471:Gastrointestinal Hemorrhage / Q000382:microbiology*; D007118:Immunoassay / Q000379:methods*; D008460:Meat / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C