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We hypothesize that YbST is a "new" (or newly recognized) enterotoxin which is responsible for the diarrheal disease seen in patients from whom the bacterium is isolated. To address the above hypothesis, we propose to further characterize the Y. bercovieri enterotoxin by partially purifying it. As a next step, the encoding gene will be cloned and sequenced. The cloned gene and/or oligonucleotides derived from the gene sequence will be used as DNA probes for evaluating the distribution and transmission patterns of Y. bercovieri. At a more basic level, these studies will provide insight into the expression and structure of a previously unrecognized enterotoxin, increasing our understanding of how bacterial pathogens cause foodborne disease.
Foodborne infections continue to be an important cause of morbidity in the modern world. Yersinia enterocolitica and Y. enterocolitica-like species are of particular concern from the standpoint of food safety because of their ability to grow and outcompete other microorganisms at refrigerator temperatures (4+C). Y. enterocolitica biogroup 3B, recently designated as a new species Y. bercovieri, has been isolated from a variety of food products (raw meat, poultry, vegetables,fruit), as well as from patients with diarrhea.
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We have recently found that it produces a potent enterotoxin (tentatively designated YbST) which stimulates massive intestinal fluid secretion in infant mice, usually resulting in death. The enterotoxin is heat-stable (remains biologically active after boiling), and is active after exposure to both very alkaline and acidic conditions. Based on molecular weight determinations, the toxin appears to be approximately twice the size of the heat-stable toxins produced by Y. enterocolitica and E. coli on a genetic level, the enterotoxin gene has no apparent homology with other known enterotoxin-encoding genes.