Evaluation of Methods for the Isolation and Detection of Escherichia coli O157:H7 from Minced Beef

Abstract

This study has evaluated enrichment and detection procedures for the isolation and detection of Escherichia coli O157:H7 inoculated into minced beef, i. e., 24hr enrichment in modified EC broth containing novobiocin (mEC+n) followed by plating onto sorbitol IPA bile salt agar (SIB), sorbitol MacConkey agar (SMAC), cefixime-tellurite SMAC (CT-SMAC) and Rainbow O157 agar, or immunomagnetic separation (IMS) followed by plating onto these four kind of media. The recovery of E. coli O157:H7 was greater on CT-SMAC than SMAC, SIB or Rainbow O157 Agar. The protocol using mEC+n incubated at 42°C, followed by IMS and inoculation onto CT-SMAC was the most succesful procedure. However, 24hr enrichment in mEC+n followed by CT-SMAC was almost as effective as the IMS method for the isolation of E. coli O157:H7.