Life Sciences Commons^™

Stress Response And Pathogenesis Of Salmonella Enterica Serovar Typhimurium, Jigna D. Shah

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Salmonella is a food-borne pathogen that leads to substantial illness worldwide. The clinical syndromes associated with Salmonella infection are enteric (typhoid) fever and gastroenteritis, in healthy humans. Typhoid fever is caused by host-adapted S. Typhi and S. Paratyphi. Gastroenteritis is caused by serovars usually referred to as non typhoidal Salmonellae (NTS). In recent years, an increasing number of outbreaks due to NTS, despite increased efforts in food safety, were reported because of persistence of Salmonella in the food chain. Thus I hypothesized that Salmonella is able to withstand stresses in the environment and treatments used during food processing …

Prevalence And Biological Control Of Salmonella Contamination In Rendering Plant Environments And The Finished Rendered Meals, Brandon Kinley

All Dissertations

Although the rendering process serves as invaluable means for the disposal of inedible animal by-products, the finished products often harbor pathogenic and opportunistic microorganisms such as Salmonella and enterococci, respectively. The temperatures used during the rendering process far exceed the heat tolerance threshold of most bacterial species, so cross-contamination from the environment and/or from the incoming raw material is the proposed source of the contamination. Research has demonstrated that the raw material coming into the rendering facility is highly contaminated with pathogenic bacteria including Salmonella. While not in a rendering facility, studies have also demonstrated that bacteria such as Salmonella …

Effect Of Anti-Lipopolysaccharide Iga Antibodies On The Virulence And Physiology Of Salmonella Enterica And Shigella Flexneri, Stephen J. Forbes

Legacy Theses & Dissertations (2009 - 2024)

Secretory IgA (SIgA) antibodies directed against the serotype-specific, O-antigen of lipopolysaccharide (LPS) are the primary determinants of mucosal immunity to enteric bacterial pathogens, including of Salmonella enterica serovar Typhimurium and Shigella flexneri. While the singular importance of SIgA in preventing enteric infections is recognized, the underlying mechanisms by which these antibodies protect the mucosal epithelium remains poorly understood. In this study, I demonstrated that Sal4, a protective, anti-LPS specific monoclonal IgA, is a potent inhibitor of S. Typhimurium flagella-based motility and type three secretion (T3S) mediated entry into epithelial cells. Sal4's effects on motility and invasion occurred rapidly (<15 min), and were independent of agglutination. I also present evidence the protective anti-LPS, monoclonal IgA, IgAC5, reduced S. flexneri T3S of IpaB and IpaC. Concurrent with the IgA-induced reduction in T3S, there was a decrease in both the proton motive force and ATP levels in both bacterial species examined. I also report that Sal4 and IgAC5 have effects on the bacterial envelope. Scanning, transmission, and cyro-electron microscopy revealed dramatic antibody-mediated alterations in the topology of the outer membrane (OM) of S.Typhimurium and S. flexneri. Furthermore, Sal4-treatment caused a ~5 fold increase in O-antigen, and elevated levels of lipid A, released into culture supernatants, consistent with the loss of LPS. Correspondingly, the OM of antibody-treated bacteria was ~50% more permeable than control cells. Based on these data, I proposed that Sal4 binding to the LPS destabilizes the outer leaflet of the OM of S. Typhimurium, thereby compromising the integrity of the bacterial envelope, disrupting bioenergetics by physical and/or mechanical stress, and arresting both flagella-based motility and T3S. This study reveals a previously unrecognized capacity of SIgA to "disarm" enteric pathogens in mucosal secretions, thereby preventing colonization and invasion of the intestinal epithelium.

Prevalence And Serovars Of Salmonella In The Feces Of Free-Ranging White-Tailed Deer (Odocoileus Virginianus) In Nebraska, David G. Renter, David P. Gnad, Jan M. Sargeant, Scott E. Hygnstrom

School of Natural Resources: Faculty Publications

To determine the prevalence and serovars of Salmonella in free-ranging deer, we cultured feces from white-tailed deer (Odocoileus virginianus) harvested by hunters during a regular firearm season in southeastern Nebraska (USA). We recovered Salmonella from 5 (1%; 95% confidence interval: 0.37– 2.20%) of 500 samples and identified four different Salmonella enterica serovars [Litchfield (1), Dessau (1), Infantis (2), and Enteritidis (1)]. Although the prevalence of Salmonella in free-ranging deer appears to be low, the serovars recovered are known to be pathogenic to humans and animals.

Methods For Detection Of Salmonella Spp., Parichaya Attaphongse

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Worldwide concern about food safety and associated health costs is increasing, and Salmonella contamination of foods is one of the most important causes of foodborne disease outbreaks. Although conventional detection methods for Salmonella offer high sensitivity and low cost, they require many different steps and are very time consuming. Ideally, methods to detect Salmonella in foods should be rapid, provide high specificity and sensitivity, be cost-effective, and low labor-intensive. Many rapid tests have been developed to address these goals, including DNA-based tests such as nucleic acid hybridization and PCR, immunoassay-based tests such as ELISA, ELF A and immunomagnetic method, and …

Rapid Detection Of Salmonella Without Enrichment, Emily J. Harrington

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Salmonella is one of the leading foodborne pathogens causing illness today. Because of this, Salmonella rapid detection methods are under immense study for use in food. The traditional method, using the Food and Drug Administration- approved Bacterial Analytical Manual procedure, takes 4-6 days for Salmonella detection in food. Other rapid methods still take at least 16 h for detection due to their enrichment steps.

The hypothesis of this study was that the use of immobilized antibodies coupled with polymerase chain reaction (PCR) can be used for the rapid capture and detection of Salmonella spp. in food without the need for …

Effects Of Conalbumin Bound Iron On The Growth Of Salmonella Paratyphi B And Salmonella Thompson, John Nicholas Mason

Dissertations and Theses

I have investigated the possibility that specific conalbumin (ovotransferrin) iron saturation levels enable less virulent strains of Salmonella to become more virulent. Iron starved cells of two pathogenic Salmonella strains, S. paratyphi B var. java and S. thompson, were cultured in iron limited media at 3 different iron conalbumin saturation levels. Results indicate that strains differ significantly at both low and high iron saturation conalbumin. These differences depict a growth advantage for S. paratyphi B which correlates with reports by the Centers for Disease Control that S. paratyphi B was 3 times more frequent in blood isolates than S. …