Salmonella species are among the major foodborne intestinal pathogens that are of public concern with respect to food safety. The ability of intestinal pathogens to resist gastric acidity corresponds to their oral infective dose (ID). The survival and lipopolysaccharide (LPS) profiles of Salmonella typhimurium grown at different pH values and to different phases of growth were examined in simulated gastric fluid (pH 1.5), ileal fluid (pH 7.0), colon fluid (pH 8.0). The survival and growth of S. typhimurium were also examined during sequential passage through all three fluids. Viable cells were rapidly reduced from 106 CFU.ml-1 to <10 CFU.ml-1 within 4 min in gastric fluid. Cells inoculated directly into ilea] and colon fluids survived and multiplied extensively. When low numbers of viable cells of Salmonella in contact with gastric fluid (0.5 min of contact) were transferred sequentially to ileal and colon fluids, only the early and late stationary phase cells were capable of recovery and growth to high numbers. The harsh environment of the gastric fluid did not change the LPS profiles of the inoculated Salmonella cells. Entrapment of S. typhimurium in calcium alginate beads and chocolate increased its survival in gastric fluid. This implies that Salmonella cells are protected from killing when ingested with food. These results may explain why Salmonella species have a very low ID when consumed as part of some contaminated food sources.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.31242 |
| Date | January 2001 |
| Creators | Igue, Patience. |
| Contributors | Idziak, E. S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Natural Resource Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001809614, proquestno: MQ70438, Theses scanned by UMI/ProQuest. |
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