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ANNUAL CONFERENCE :: Abstract Library
Abstract Library
2003 Conference Abstract
| Type of Submission |
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Submission Type: |
Poster Presentation |
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Subject Category: |
Veterinary Microbiology |
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| Session Information |
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Presentation Date: |
May 26, 2003 |
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Abstract ID: |
G13 |
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Session: |
Poster 1 |
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Time: |
14:00 |
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| Presenting Author |
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| Other Authors |
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S. MESSIER, Faculty of Veterinary Medicine (GREMIP)
L. SAUCIER, Food Research and Development Centre
G. PIETTE, Food Research and Development Centre
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| Title |
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In vitro digestion of E. coli O157:H7 in dry sausage. Key words: Escherichia coli O157:H7, dry sausage, survival, in vitro digestion, synthetic digestive fluid |
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| Abstract Text |
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An in vitro methodology which closely mimics in vivo human upper gastrointestinal transit was elaborated to evaluate the risk attributed to an accidental consumption of dry sausages contaminated with Escerichia coli O157:H7. Sausages inoculated during formulation with ca. 2X107 CFU/g of pure cultures of E. coli O157:H7 were sliced and stomached in artificial saliva to simulate mastication. Artificial gastric juice pre-adjusted to pH 2.0 was then added, which caused an initial rapid decrease in pathogen numbers, followed by stabilization. Following a 2-h challenge, the pH of the juice was raised to 8.0, and synthetic pancreatin and bile extract were added to mimic the passage into the intestinal phase. Bile extract and proteolytic enzymes added did not adversely affect the E. coli cells survival since, under the neutral pH conditions, the simulated pancreatic juice supported a gradual growth of bacterial populations, which surpassed the initial levels they had in saliva. Since the acidic pH was the critical factor delimiting cell growth, we performed digestion tests under controlled pH conditions in which samples were taken from the artificial gastric juice at 30-min intervals and transferred into the intestinal phase to mimic the gastric emptying. Concurrently, the pH of the remaining gastric fluid was reduced to 3, 2.5 and 2 units respectively, to mimic the gradual re-acidification of the stomach content after ingestion of a meal. The relatively severe acidic conditions caused cell injury, but no cell destruction occurred. However, growth in pancreatic juice was slower and slower as the cells stayed longer in the gastric environment, at an increasingly low pH. Thus, digestion offers no real challenge for E. coli O157:H7, since ingested cells survive the gastric acidity and regrow in the intestine. |
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