A multiplex polymerase chain reaction (PCR) assay was designed to simplify detection of Escherichia coli O157:H7 and to identify the H serogroup and the type of Shiga toxin produced by this bacterium. Primers for a plasmid-encoded hemolysin gene (hly933), and
chromosomal flagella (fliCh7; flagellar structural gene of H7 serogroup), Shiga toxins (stx1, stx2), and attaching and effacing (eaeA) genes were used in a multiplex PCR for coamplification of the corresponding DNA sequences from enterohemorrhagic
E. coli (EHEC) O157:H7. Enrichment cultures of ground beef, blue cheese, mussels, alfalfa sprouts, and bovine feces, artificially inoculated with various levels of E. coli O157:H7 strain 933, were subjected to a simple DNA extraction step prior to the PCR, and the resulting amplification
products were analyzed by agarose gel electrophoresis. Sensitivity of the assay was ≤ 1 CFU/g of food or bovine feces (initial inoculum level), and results could be obtained within 24 h. Similar detection levels were obtained with ground beef samples that underwent enrichment culturing
immediately after inoculation and samples that were frozen or refrigerated prior to enrichment. The multiplex PCR facilitates detection of E. coli O157:H7 and can reduce the time required for confirmation of isolates by up to 3 to 4 days.
Document Type: Research Article
Agricultural Research Service, Eastern Regional Research Center, U.S. Department of Agriculture, 600 E. Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA 2:
University of Naples Federico II, Department of Pathology, Prophylaxis, and Food Inspection, Via F. Delpino 1, 80137 Naples, Italy
Publication date: August 1, 2000
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