| Summary: | 碩士 === 國立中興大學 === 微生物暨公共衛生學研究所 === 103 === Salmonella is an intracellular pathogen in macrophages. The bacterium could become multi-drug resistant(MDR) while carrying Salmonella genomic island1(SGI1). Systematic infectionis frequently associated with MDR Salmonella in human clinical cases. S. serotype 4,[5],12:i:-, antigenically similar to S. Typhimurium but lack of second type flagella antigen, is recently identified to be an emerging humanpathogen. This study was conducted to compare invasiveness and proinflammatory responses between these two serotypes using Raw 264.7 macrophages. The results showed that non-SGI1 S. Typhimurium strains were more invasive than the ones with SGI1 (p<0.05). Macrophages infected by non-SGI1 S. Typhimurium strains were with higher survival percentage than the SGI1 strains (p<0.05). Furthermore, significantly lower levels of proinflammatory cytokines: TNF-α (at 8, 24 hr), IL-1β (at 4, 8, 24 hr), IL-6 (at 0, 4, 24 hr) and NO (at 4, 8, 24 hr),were observed in SGI1 than non-SGI strains. Besides, higher levels of proinflammatory cytokine IFN-γ were found in S. 4,[5],12:i:- strains, comparing to S. Typhimurium with non-SGI1. The findings suggest that S. Typhimurium carrying SGI1 may be less invasive and induce less proinflammatory responses than the non-SGI1 one. The results may suggest that SGI1 S. Typhimurium may have higher cell-killing ability to cause macrophage death, which resulted in the lower invasion and proinflammatory cytokine levels. Comparing to S. Typhimurium, higher level of IFN-γ induced by S. serotype 4,[5],12:i:-, implied that more effective early immune response may limit S. serotype 4,[5],12:i:- infection clinically.
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