Browsing by Subject "Clostridium perfringens"
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Item Enhancing Chicken Mucosal IgA Response Against Clostridium Perfringens a-toxin(2012-07-27) Chen, Chang-Hsin 1977-Necrotic enteritis (NE) is an economically important enteric disease of broiler chicken primarily caused by a-toxin (Cpa) secreted by C. perfringens type A. Mice immunized with recombinant C-terminal domain of Cpa (CpaCD) had transient and fewer localized lesions upon challenge with C. perfringens type A. These results demonstrate the usefulness of CpaCD as an immunogen for vaccine development against NE for chickens. Chicken CD40 (chCD40) is mainly expressed on the surface of chicken antigen-presenting cells (APCs), and the interaction of chCD40 and chCD40L (natural ligand for chCD40) provides crucial activation signals for chicken B-cells. A hypothesis was proposed that in ovo vaccination with an adenovirus-vectored CpaCD vaccine capable of targeting immunogen to APCs through the CD40 pathway will improve protection against NE in chickens. One agonistic monoclonal anti-chCD40 antibody (designated 2C5) was produced and characterized. 2C5 not only detected expression of chCD40 on chicken APCs, but also induced NO synthesis in chicken HD11 macrophages and enhanced proliferation of serum-starved chicken DT40 B-cells. This demonstrated substantial functional equivalence of 2C5 with chCD40L. The potential of 2C5 as an immunological adjuvant was further assessed by targeting a hapten to chicken APCs in hopes of enhancing an effective IgG response. Seven-week old chickens were immunized subcutaneously once with a complex consisting of 2C5 and peptide, and relative quantification of the peptide-specific IgG response showed that this complex was able to elicit a strong IgG response as early as four days post-immunization. This demonstrates that CD40-targeting antigen to chicken APCs can significantly enhance antibody responses and induce immunoglobulin isotype-switching. An agonistic anti-chCD40 single-chain variable fragment (designated DAG1) was combined with an adenoviral delivery system to create a vaccine, Ad-(DAG1-Cp aCD-FLAG), for in ovo administration. The efficacy of in ovo vaccination of broilers with Ad-(DAG1-Cp aCD-FLAG) in controlling NE was evaluated by C. perfringens type A challenge at 18 days post-hatch. Neither statistically significant IgA / IgG response nor protection against C. perfringens type A challenge was found in the vaccinated birds. These preliminary data suggest that a super-optimal dose of Ad-(DAG1-Cp aCD-FLAG) may be the main issue, because Cpa-specific B-cells may undergo apoptosis through the CD40 pathway.Item Evaluation of agricultural disinfectants and necrotic enteritis preventatives in broiler chickens(2009-05-15) Stringfellow, Kendre DuaronThe objective of this study was to determine the effect of time, temperature and organic matter on disinfectant efficacy. Staphylococcus aureus (SA) and Salmonella Typhimurium (ST) were used as organisms to represent Gram positive and Gram negative bacteria, respectively, commonly found in poultry housing. Three independent experiments evaluated the effect of temperature, time, and organic matter on the efficacy of working concentrations of disinfectants against representative organisms found in commercial poultry housing. Quaternary ammonium, chlorhexidine, phenolic and binary ammonium based solutions represented disinfectants commonly used within the poultry industry. Results from these experiments indicated that long term storage of disinfectants will reduce their efficacy against SA. However, a reduction (p ? 0.05) in efficacy was observed with the phenolic compound against ST at elevated temperatures. Following the inclusion of organic matter (OM), reduced (p ? 0.05) efficacy of all disinfectants was observed in a dose dependent manner against both organisms, with the exception of the phenolic compound against SA. Fresh disinfectant performed better (p ? 0.05) in the presence of OM than 30 wk old disinfectant. These results emphasize the need to use fresh disinfectants and that OM should be removed prior to disinfection. We also evaluated the effect of bismuth citrate, lactose and citric acids on the development of necrotic enteritis in broilers. Clostridium perfringens? associated necrotic enteritis in poultry causes significant loss and increased morbidity in the industry. Due to the reduced usage of antibiotic growth promoters, the incidence of necrotic enteritis has increased. These experiments evaluated different levels of bismuth citrate and bismuth citrate with lactose or citric acid added, on lesion development, bacterial intestinal colonization of C. perfringens and pH levels in the gut of broilers orally challenged with C.perfringens. Results from this investigation indicate that bismuth citrate at 100 ppm and 200 ppm caused a reduction (p ? 0.05) in C. perfringens colonization and intestinal lesion development. The addition of dietary lactose to bismuth citrate enhanced the effect of bismuth citrate on intestinal lesion development. These data suggest that bismuth citrate alone or in combination with dietary lactose will reduce intestinal lesion development in broilers with necrotic enteritis.Item Heat resistance and outgrowth of clostridium perfringens spores as affected by the type of heating medium, and heating and cooling rates in ground pork(2009-05-15) Marquez Gonzalez, MayraThe survival and germination of Clostridium perfringens spores in different heating media and at different heating rates was studied to determine the fate of C. perfringens spores during abusive cooking and cooling of pork products. The heat resistance (HR) of C. perfringens spores from three strains that were either previously heat shocked (HS) or non-heat shocked (NHS) was determined individually and as a cocktail in phosphate buffer solution (pH 7.4) (PBS), beef gravy (BG), ground pork (GP) and cured ground pork (CGP) at 75?C. The effect of the heating rate on HR, germination and outgrowth of C. perfringens spores in CGP was determined by increasing the temperature from 20 to 75?C at a rate of 4, 8, and 12?C/h prior to heating and holding at 75?C for 48 h. Heating rates at 4?C/h in GP and CGP were repeated with additional cooling from 54.4 to 7.2?C within 20 h (temperature abuse). Linear survival curves were observed on NHS spores in the four heating media, whereas HS spores showed linear curves when heated in PBS and BG, and biphasic curves when heated in GP and CGP. In general, HS spores were more heat sensitive than NHS spores. NHS spores heated in GP had greater HR than spores heated in CGP, BG or PBS. There were no significant differences (P>0.05) on the HR of C. perfringens spores in CGP heated from 20 to 75?C at 4, 8, or 12?C/h. Heating rates of 8 and 12?C/h showed no difference in germination and outgrowth of inoculated spores, whereas at 4?C/h, growth of C. perfringens occurred between 44 and 56?C. Temperature abuse during cooling of GP resulted in 2.8 log CFU/g increase of C. perfringens counts. In CGP, C. perfringens counts decreased by 1.1 log CFU/g during cooling from 54.4 to 36.3?C and then increased by 1 log CFU/g until the product reached 7.2?C. However, with an initial inoculum in raw CGP of 5 log CFU C. perfringens spores/g, C. perfringens counts did not exceed 3.4 log CFU/g during a 20 h abusive cooling. These results suggest there is no risk associated with C. perfringens in cured pork products under the conditions tested. Results from the present study indicate that different behavior may be expected with different meat products.