An Improved Screening Method for the Detection and Isolation of Escherichia coli 0157:H7 From Meat, Incorporating the 3M Petrifilm™ Test Kit - HEC - for Hemorrhagic Escherichia coli 0157:H7.

A screening method was devised incorporating a commercially available reactive disc blot ELISA for Escherichia coli 0157 antigen, into a cultural screening program for the isolation of E. coli 0157:H7 from meat and poultry products. The method includes the inoculation of a raw or cooked meat sample into an enrichment broth, incubation with shaking at 37°C for 6 to 8 h, followed by inoculation of 3M Petrifilm™ E. coli Count plates with dilutions of the enrichment culture. The Petrifilm plates were incubated at 42°C for 18 h and tested for the presence of the 0157 antigen. The enrichment cultures were reincubated static at 35°C after the initial shaken incubation. Isolation was attempted from the positive Petrifilm plates by both a direct picking and streaking method and by the 3M Prompt™ isolation method. Isolation also was attempted from the 24-h enrichment cultures by spread plating serial dilutions on 150 × 15 mm MacConkey sorbitol agar (MSA) and MSA with 5-bromo-4-chloro-3-indoxyl-β-D-glucuronic acid cyclohexylammonium salt (BCIG). This fast and efficient screening procedure identifies negative and presumptive positive samples in 26-28 h. Isolation and confirmation of the presumptive positive isolates require an additional 3 to 4 d.