Detection of Escherichia coli O157:H7 in ground beef in eight hours

A new method involving enrichment and immuno-polymerase chain reaction is presented for rapid and sensitive detection of Escherichia coli O157:H7 in ground beef. The bacteria in the spiked beef sample were enriched in a non-selective medium for 250 min and the E. coli O157:H7 cells were captured rapidly from the culture medium, using magnetic beads coated with E. coli O157-specific antibody. Partial stretches of sequences encoding Shiga toxins (Stx1 and Stx2) were amplified by the polymerase chain reaction and detected by agarose gel electrophoresis. Detection of a 215/212-base pair amplicon indicated contamination of the test sample with E. coli O157:H7. The method enabled detection of a single colony-forming unit of E. coli O157:H7 conclusively in 8 h. The suitability of the method to real life pathogen monitoring applications was demonstrated by accurate confirmation of E. coli O157:H7 in coded culture-positive samples of naturally contaminated ground beef and hamburger patties. (C) 1998 Elsevier Science B.V. All rights reserved.