Regulation of Salmonella virulence by environmental factors present in the chicken cecum and crop /
A number of environmental conditions relevant to the chicken intestinal tract were measured for their ability to affect Salmonella invasion and regulation of invasion genes. S. typhimurium or S. enteritidis with a hilA or invF-lacZY fusion were used to determine the effects on invasion gene expressi...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=730319021&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | A number of environmental conditions relevant to the chicken intestinal tract were measured for their ability to affect Salmonella invasion and regulation of invasion genes. S. typhimurium or S. enteritidis with a hilA or invF-lacZY fusion were used to determine the effects on invasion gene expression. At pH 6, maximal hilA and invF gene expression was observed within the first hour of growth in the presence of acetate, propionate, or butyrate. This expression was 1.4 to 3.7-fold higher than the LB control. The expression of hilA was 2.9-fold higher in LB broth diluted 1:5 compared to undiluted LB broth. Addition of 0.2% glucose, fructose, or maltose to the media reduced hilA expression 1.5 to 2-fold. Addition of 0.2% Casamino acids, arabinose, fucose, or lactose had little effect on hilA expression. S. typhimurium invasion of cultured HEp-2 cells was decreased when Salmonella was grown for 4 h in LB broth supplemented with propionate, butyrate, or a mixture of the three organic acids. Acetate had little effect on cell-association and the ability to invade cultured HEp-2 cells. The regulation of cell-association and invasion by short-chain fatty acids (SCFA) was dependent on the concentration and the DH of the medium. Force molt induced in 50 week old Leghorn hens by 9 day feed withdrawal changed the crop environment. On days 4 and 9 of molt, the numbers of lactobacilli, and the concentrations of lactate, acetate, propionate, and butyrate in the crops decreased significantly (P < 0.05) while the crop pH increased significantly in molted hens compared to the controls. S. enteritidis crop and cecal colonization in addition to spleen and liver invasion were significantly increased in the molted hens compared to the controls. In vitro, the expression of hilA was 1.6 to 2.1-fold higher in the crop contents from molted birds compared to control birds. This research suggests that SCFA in the cecum and the changes in crop environment, such as pH and lactate concentrations, that occur during force molt have the potential to regulate the pathogenesis of Salmonella. |
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| Item Description: | Vita. "Major Subject: Poultry Science". |
| Physical Description: | x, 127 leaves ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 102-126). |