Since 1982, E. coli O157:H7 has been linked to numerous foodborne outbreaks and sporadic cases.

Since 1982, E. coli O157:H7 has been linked to numerous foodborne outbreaks and sporadic cases of hemorrhagic colitis and hemolytic uremic syndrome. The most common epidemiologically associated food is ground beef. Scientists have discovered oligonucleotide sequences, primers that were derived from DNA sequences contained within a 60-MDa plasmid, that specifically amplify a DNA fragment of the plasmid found in all strains of the bacteria. The polymerase chain reaction (PCR) can amplify just a few copies of the target DNA, thus eliminating the need for a time-consuming enrichment step. Various techniques, including agarose gel electrophoresis or DNA hybridization with calorimetric or chemiluminescent detection, can detect the PCR products. This approach requires only a small sample and just a fraction of the time required by traditional techniques. Protocols incorporating these DNA sequences are amenable to automation. The rapid testing of large numbers of samples would be possible. Such tests can be used to detect the organism in foods such as ground beef, and in cattle fecal specimens. The tests can potentially be designed to detect the pathogen on beef carcasses during inspection. Researchers have developed a multiplex PCR assay for identifying E. coli O157:H7. The technology is patented (US 5,652,102) and is available for licensing. Contact: C.G. Crawford, USDA-ARS Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038. Phone: [phone]. Fax: [phone]. Email: [e-mail].