KMID : 0893420150160020187
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Journal of Veterinary Science 2015 Volume.16 No. 2 p.187 ~ p.194
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The role of rpoS, hmp, and ssrAB in Salmonella enterica Gallinarum and evaluation of a triple-deletion mutant as a live vaccine candidate in Lohmann layer chickens
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Cho Young-Jae
Park Yoon-Mee Barate Abhijit Kashinath Park So-Yeon Park Hee-Jeong Lee Mi-Rae Truong Quang Lam Yoon Jang-Won Bang Iel-Soo Hahn Tae-Wook
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Abstract
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Salmonella enterica Gallinarum (SG) causes fowl typhoid (FT), a septicemic disease in avian species. We constructed deletion mutants lacking the stress sigma factor RpoS, the nitric oxide (NO)-detoxifying flavohemoglobin Hmp, and the SsrA/SsrB regulator to confirm the functions of these factors in SG. All gene products were fully functional in wild-type (WT) SG whereas mutants harboring single mutations or a combination of rpoS, hmp, and ssrAB mutations showed hypersusceptibility to H2O2, loss of NO metabolism, and absence of Salmonella pathogenicity island (SPI)-2 expression, respectively. A triple-deletion mutant, SG¥Ä3 (SG¥ÄrpoS¥Ähmp¥ÄssrAB), was evaluated for attenuated virulence and protection efficacy in two-week-old Lohmann layer chickens. The SG¥Ä3 mutant did not cause any mortality after inoculation with either 1 ¡¿ 106 or 1 ¡¿ 108 colony-forming units (CFUs) of bacteria. Significantly lower numbers of salmonellae were recovered from the liver and spleen of chickens inoculated with the SG¥Ä3 mutant compared to chickens inoculated with WT SG. Vaccination with the SG¥Ä3 mutant conferred complete protection against challenge with virulent SG on the chickens comparable to the group vaccinated with a conventional vaccine strain, SG9R. Overall, these results indicate that SG¥Ä3 could be a promising candidate for a live Salmonella vaccine against FT.
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KEYWORD
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live attenuated vaccine, oxidant response genes, protection, Salmonella enterica Gallinarum, virulence
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