Detection of enterohaemorrhagic Escherichia coli (EHEC) in raw meat and raw meat sausages - Comparative evaluation of different methods

Eighty-one beef and pore meat: samples and 41 samples from raw sausages wer e examined for the presence of enterohaemorrhagic Escherichia coli (EHEC). Different detection and enrichment procedures for EHEC were compared. All s amples were investigated by PCR methods specific for different types of shi ga-toxin (stx) genes. Three (2.5 %) of the 122 samples were found positive in two different stx-specific PCRs and in the verocell toxicity assay. One of the two employed stx-PCR methods gave more specific results than the oth er. A liquid medium containing vancomycin, cefixime and cefsulodin which wa s originally developed for selective enrichment of EHEC O157 was not suitab le for enrichment of non-O157 EHEC strains. Enterohaemolysin-agar containin g 8mg/Lvancomycin was used as a selective medium for plating Gram-negative bacteria from meat samples. However, higher concentrations than 8 mg/L vanc omycin should not be used because with these a false-positive hemolysis tva s observed with some bacteria. The O157 CD-Seiken-Test was used for specifi c enrichment and detection of EHEC O157 from meat samples. With this method , two colonies of EHEC O 157/10 g meat were still detectable. The test empl oys an immunomagnetic separation (IMS) step for concentration of E. coli O1 57 bacteria. However, high amounts of Eat: in the sample hindered the perfo rmance of the IMS.