Browsing by Subject "Salmonella Typhimurium"
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Electron Beam As A Next Generation Vaccine Platform: Microbiological And Immunological Characterization Of An Electron Beam Based Vaccine Against Salmonella Typhimurium(2014-04-16) Praveen, ChandniVaccines against infectious diseases are a corner stone of public health globally. Vaccine technology based on attenuation, conventionally ?killed? or cellular sub-units suffer from significant drawbacks. Live attenuated vaccines impart strong cellular and humoral immune response compared to inactivated or subunit vaccines, but there is an increased risk of infection from the potential virulence reversion in such formulations. The current study explores the use of eBeam irradiation as a novel tool for vaccine generation. The value of eBeam based vaccines is that, they combine the safety of ?killed? vaccines, yet retain the immunogenicity of ?attenuated? vaccines. The principle of eBeam vaccine is eBeam irradiation will only irreversibly damage the target microorganism?s nucleic acid without modifying the antigenic properties of surface macromolecules. In this study microbiological characterization of eBeam based S. Typhimurium (EBST) vaccine was carried out. The immunological correlates of protection induced by the EBST in dendritic cell (DC) (in vitro) and mice (in vivo) model were also assessed. Results showed that eBeam inactivation preserved the potent proinflammatory and immunogenic properties of S. Typhimurium. The EBST remained metabolically active yet unable to multiply under favorable in vitro and in vivo conditions. The EBST potently stimulated innate pro inflammatory response (TNF?) and maturation (MHC-II, CD40, CD80 and CD86) of DC. Immunostimulatory potential of EBST was on par with live Salmonella, and most importantly on par with a commercial Salmonella vaccine. Results from the mice challenge studies demonstrated the involvement of CD4+T cells as key player in cell mediated immune response of EBST immunized mice, triggering the production of Th1 cytokine IFN?. This indicates the stimulation and development of robust Salmonella specific T cell response similar to that caused by the live attenuated vaccine (AroA- ST) formulation. The colonization of virulent Salmonella was also reduced in EBST immunized mice similar to AroA immuninized mice. The EBST retained stable immunogenic properties for several months at room temperature, 4?C, - 20?C and also after lyophilization. These findings highlight the potential of eBeam technology as an effective and affordable next generation vaccine platform to address global public health issues.Item Epidemiology of Bacterial Food-borne Pathogens: Linking Intermittent Pathogen Shedding and Transmission in Their Animal Hosts(2013-04-30) Gautam, RajuMost bacterial foodborne pathogens are shed intermittently from their animal hosts and are able to grow and persist in the environment. Cattle and pigs constitute the major animal reservoirs for these pathogens. The overall objective of this dissertation research was to improve understanding of the role of intermittent shedding and environmental persistence in the transmission and maintenance of Escherichia coli O157:H7 and Salmonella Typhimurium in their animal host populations. This objective was addressed through five interdepended studies. The study in Chapter II, describes the transmission of E. coli O157:H7 in a dairy herd using mathematical modeling that includes indirect transmission from the contaminated environment. The model predicts that the elevated ambient temperature during summer, together with the availability of large amount of drinking water per cattle, are the major factors for increased pathogen load in water and high prevalence of E. coli O157:H7 in cattle populations. The second study, in Chapter III, determined the variation in water-to-cattle ratios among feedlot pens and evaluated the association with the pen level management and environmental factors. Water-to-cattle ratio was found to vary greatly between feedlots and pens with lower water-to-cattle ratios on average had cooler drinking water. The study in Chapter IV, used a compartmental mathematical model of infection transmission, to evaluate the effect of cleaning on Salmonella Typhimurium control in a grower-finisher pig herd. Cleaning alone was not found to be an effective measure of control unless combined with other measures to reduce the level of bacterial shedding. The study in Chapter V, developed the multi-state Markov chain model to describe the fecal shedding pattern of three E. coli O157:H7 strains in cattle. One strain was not detected to shed, while the other two strains had on average different durations of host colonization, albeit not at the statistically significant level. The study in Chapter VI, used an experimental infection transmission approach to estimate and compare transmission rates for three different strains of E. coli O157:H7 in steers. The results revealed that the transmission rate of E. coli O157:H7 increases significantly with increasing levels of environmental contamination. Collectively, the five studies have highlighted the role of these pathogen characteristics in their transmission. The improved understanding of these characteristics will allow for better design of control measure to ensure food safety.Item The use of xylitol to minimize contamination of beef carcass surfaces with salmonella typhimurium and escherichia coli o157:h7(Texas A&M University, 2006-08-16) Greiner, Steven ThomasEffects of a 10% xylitol solution (X) on adhesion of Escherichia coli O157:H7 and Salmonella serotype Typhimurium to meat surfaces were examined utilizing three approaches. In Experiment 1, rifampicin-resistant strains of E. coli O157:H7 and S. Typhimurium were dispersed in xylitol or a peptone solution (containing approximately 8.9 mean log per ml of each pathogen) and used to inoculate beef outside round meat surfaces. Samples were then rinsed with water or not rinsed in a 2X2 factorial arrangement. No interaction existed between inoculum type and post-inoculation treatments (P > 0.84). Incubation of pathogens in peptone or xylitol had minimal impact on pathogen adhesion (P > 0.76). Rinsing reduced counts by approximately 0.5 log CFU/cm2 (P < 0.01). Experiment 2 meat samples received a pretreatment of a water rinse, xylitol, or no rinse, followed by inoculation with pathogens dispersed in peptone solution (containing approximately 8.6 log mean log per ml of each pathogen). Samples received a post-inoculation treatment of a water rinse, xylitol rinse or no rinse in a 3X3 factorial arrangement. No interactions between pre- and post-inoculation factors were observed for surface pathogen load (P > 0.50). Post-inoculation rinsing reduced counts by approximately 0.5 log CFU/cm2 (P < 0.01) with no difference between water and xylitol (P > 0.64). Experiment 3 carcass surfaces were inoculated with pathogens at an initial level of 5.5 log CFU/cm2 and received a hot (35??C) water wash, 2.5% L-lactic acid spray, 10% xylitol spray, lactic acid + xylitol or hot water + xylitol. Pathogen counts were taken at 0 and 24 h post treatment. Lactic acid treatments reduced Salmonella by 3.3 log CFU/cm2 at 0 h (P < 0.01) and by 2.6 log CFU/cm2 after 24 h (P < 0.02). Hot water treatments reduced Salmonella by 1.5 log CFU/cm2 at 0 h (P < 0.07). Xylitol did not minimize pathogens (P > 0.62) nor did it increase effectiveness of other treatments. These data indicate that xylitol is ineffective at preventing E. coli O157:H7 and S. Typhimurium adhesion to meat surfaces.Item Validation of chemical and non-chemical antimicrobial interventions applied pre- and post-chilling to reduce microbial populations in broiler carcasses(2009-05-15) Molina, Veronica AlejandraHigher risks of food-borne illness associated with increased consumption of poultry products make it necessary to identify potential sources of contamination and apply intervention strategies that will prevent or minimize the risk of contamination during processing. This study investigated the effects of chemical and natural decontamination treatments including sprayed application of acidified calcium sulfate (ACS) in combination with -polylysine (EPL), dry-rubbing kosher salt coating and molten paraffin wax dipping application on microbial populations of broiler carcasses and parts. Treatments were evaluated for their effectiveness in reducing the numbers of artificially inoculated rifampicin resistant Salmonella Typhimurium strain NVSL 95-1776 on the skin surface of bone-in chicken breasts. General model procedures were used to find statistical differences (P<0.05) and separation of means was done with least square means using SAS 9.1. Chemical interventions (ACS + EPL) caused an overall reduction of ~0.65 CFU/ml of rifampicin resistant Salmonella Typhimurium populations in inoculated chicken breasts. Similar reductions were observed in validation experiments in whole carcasses when compared to post-eviscerated control samples as well as post chilled treated samples when compared to post-chill controls. Kosher salt interventions caused ~1.15 CFU/ml log reductions in rifampicin resistant Salmonella Typhimurium loads. Significant differences (>2 log reductions) were also observed in validation trials in both pre- and post-chilled samples when compared to non-treated pre- and post-chilled controls. Only for psychrotrophic counts, chilled and post-chill interventions did not have a significant effect (P>0.05). The use of molten paraffin wax caused <0.51 CFU/ml log reductions on rifampicin resistant Salmonella Typhimurium in chicken breasts. In addition, drip loss on kosher treated samples was 53.8% lower than non-treated counterparts. However, kosher salt application caused a decrease in lightness (*L values) and yellowness (*b values) on treated carcasses when compared to controls, redness (*a values) were not significantly affected. Results indicate that the combined use of ACS and EPL at the stated conditions and the coating application of kosher salt on broiler carcasses significantly reduce pathogen contamination and microbial indicator loads, thus providing an alternative validated antimicrobial intervention for potential use by the poultry industry.