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S. F. AL-KHALDI, Center for Food Safety & Applied Nutrition, U.S. Food & Drug Administration, Office of Nutritional Products, Labeling & Dietary Supplements, 5100 Paint Branch Pkwy., HFS-517, College Park, MD 20740-3835 Because of rapid changes in our lifestyle, current and future outbreaks require new technologies to provide fast and specific methods for the detection of potentially dangerous pathogenic bacteria in food. Several emerging high-throughput technologies for gene identification are on the horizon involving genomics. A DNA microarray method is a good example for identifying the presence of several virulence genes for many bacterial strains simultaneously. DNA microarray chips are currently being developed to identify virulence genes of Clostridium perfringens and Yersinia enterocolitica. The chips were designed to have at least three to five individual oligonucleotide probes (oligoprobes) that are complementary to the unique sequences of each toxin gene. The oligoprobes were immobilized on a glass surface slide and multiplex PCR reactions were used to amplify target regions of all virulence genes. Single-stranded DNA (ssDNA) samples for microarray analysis were prepared by following a primer extension of amplicons in the presence of one primer. Fluorescent moieties (Cy5 or Cy3) were incorporated into the ssDNA by chemical modification. The presence of toxin genes was established by hybridization of the fluorescently labeled ssDNA samples to the microarray gene-specific oligoprobes. The technology seems to be very specific and perhaps more reliable compared with multiplex PCR gel electrophoresis.
Session 20, Application and use of genomics in food microbiology
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