| Summary: | 碩士 === 國立嘉義大學 === 微生物與免疫學系研究所 === 98 === Salmonella Pullorum is the pathogen for Pullorum disease, which causes high mortality of the infected young chicks. S. Choleraesuis and S. Typhimurium are the most commonly serotypes isolated from pigs. Because of the increase of drug resistance problems of these Salmonella, the vaccine developments and studies are important issues.
We collected 51 S. Pullorum strains, including 46 strains from Canada, 2 strains from USA and 3 strains from Taiwan. Plasmid analysis showed that all USA and Taiwan isolates and 97.8% isolates from Canada harbored an 87 kb virulence plasmid. Susceptibility to 10 antimicrobials was performed by disk diffusion method. In Canada, all strains were susceptible to ampicillin, chloramphenicol, nalidixic acid and tetracycline. 41.3-84.8% strains were resistant to penicillin, streptomycin, cefuroxime, sulfamethoxazole and trimethoprim; only one strain(2.2%) was resistant to cephalothin or gentamicin. In addition, 69.6% strains were multiple drug resistance (MDR), 30.2% of isolates were resistant at least to 4 antimicrobials and showed an increasing trend from 1994 to 2004. Strains from USA or Taiwan were resistant to cephalothin or streptomycin. PFGE patterns included type 1a-1m, 2a, 2b and 3-8. The major PFGE patterns in Canada and USA were pulsotype 1. In Canada, pulsotype 1a and 1b were the major PFGE patterns in 1994 and 2004. The major genotype in Taiwan was type 2.
On the other hand, to evaluate the effects of S. Choleraesuis and Typhimurium on the immunce responses of pig the IFN-γ, IL-1, IL-6 and IL-10 expression of swine peripheral blood mononuclear cells (PBMCs) and polymorphonuclear neutrophils (PMNs) were determined after pigs fed with different vaccine strains S. Typhimurium (ST) OU5048 and S. Choleraesuis (SC) OU7266 or SC2284 and challenge with S. Choleraesuis CN36. 20 pigs were divided into five groups, 4 pigs per group. 3 groups were separately oral fed with vaccine strains ( OU5048, OU7266 or SC2284) respectively and the control group with 8 pigs in total was subdivided into two groups with or without challenging CN36. 2 weeks after vaccination, pigs were challenged with CN36.The results showed that fed intake was reduced in S. Choleraesuis groups, but it did not affect the growth of pigs. Salmonella prevalence was different among treatments in feces collected by rectal swab. Further, we analyzed the change in cytokine expression. 1) Before challenge, IFN-γ, IL-1α and IL-6 expressions of PBMCs and PMNs were increased in all SC groups. In the same time, IFN-γ, IL-1α and IL-6 expressions were higher in SC groups than in ST group. IL-10 expression of PBMCs and PMNs was increased in all vaccine groups. 2) After challenge with CN36, IL-10 level was up-regulation in CN36 challenge group, but IL-6 expression was down-regulation. In IFN-γ and IL-1α expression levels, down-regulation was observed in PBMCs, but up-regulation was observed in PMNs. In addition, after challenge in pigs with vaccine treatments, IFN-γ, IL-1α and IL-6 expressions in PBMCs were increased and IL-10 expression was decreased in PBMCs and PMNs.
In conclusion, most S. Pullorum strains harbored an 87 kb virulence plasmid and were MDR strains with a gradual increase and the genotype was related to isolation regions and timing. S. Choleraesuis and S. Typhimurium vaccines induced separate immunce responses of pig before and after challenge with S. Choleraesuis CN36. Different serovar strains induced different immune responses.
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