Polymacron™ Enzyme Immunoassay System for Detection of Escherichia coli O157 Inoculated into Foods†

Abstract

A rapid and simple enzyme immunoassay system was developed for detection of the food-borne pathogen Escherichia coli O157. This system is based on the use of anti-E. coli O157 antibody-coated Polymacron™, an inexpensive macroporous polyester fabric, as a high-surface-area immunoadsorbent for the rapid capture and subsequent immunoenzymatic detection of E. coli O157 antigens extracted from test samples by heating at 100°C for 10 min in the presence of sodium cholate. A dot blot format was used which facilitated the assay of multiple samples. The method was specific for all strains tested bearing the O157 and related antigens (e.g., group N Salmonella), giving positive reactions in the assay of pure cultures of 29 E. coli O157:H7 strains, one E. coli O157:H12, one E. coli O157:NM (nonmotile) and one Salmonella urbana strain, but not in the assay of a variety of other gram-negative and gram-positive bacteria. The method permitted the detection of ca. 400 E. coli O157:H7 CFU in a 5-μl spot applied to Polymacron™, and of as few as 0.4 CFU of E. coli O157:147 cells per g inoculated into ground beef samples, which were assayed after overnight enrichment.