Serological inductivity of S.Enteritidis FliC-specific 9 kDa polypeptide in laying hens infected with S.Enteritidis.

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Specific antibody levels of laying hens and young chickens experimentally infected with Salmonella Enteritidis were evaluated by enzyme-linked immunosorbent assays (ELISAs) with two different antigens, deflagellated S.Enteritidis whole cell (DEWC) and S.Enteritidis FliC-specific 9 kDa polypeptide (SEP9). Infected laying hens excreted S.Enteritidis throughout the experimental period, and the DEWC-specific antibody titers were significantly higher than the uninfected group. The SEP9-specific antibody was detected in spray-inoculated young chickens but oral-inoculated young chickens. Compared with greatly high SEP9-specific antibody levels of vaccinated laying hens, no response was observed in orally infected hens. These results suggest that the DEWC-specific antibody will serve as an effective indicator of S.Enteritidis infection, especially for non-vaccinated layer flocks, and that the SEP9-specific antibody will serve as a valuable monitoring tool for status of S.Enteritidis vaccinatio … More n on a flockwide basis, independent of S.Enteritidis infection, as S.Enteritidis discontinues expressing SEP9 once it has crossed the intestinal barrier.Japanese layer farms were surveyed for Salmonella Enteritidis infection and vaccination with specific antigens for egg yolk antibodies with the use of infection-specific antigen, deflagellated S.Enteritidis whole cell (DEWC), and vaccination-specific antigen, S.Enteritidis FliC-specific 9kDa polypeptide (SEP9). Eggs produced by 201 farm flocks with more than 100,000 laying hens were purchased at wholesale markets chosen randomly throughout Japan and tested for ELISA titers of specific antibodies. The percentages of farm flocks with a mean ELISA titer of over 0.1 were 56.2% (113 of 201) in DEWC-ELISA and 22.3% (45 of 201) in SEP9-ELISA. Flocks indicating high titers in SEP9-ELISA always showed high titers in DEWC-ELISA. Because both specific antibody titers of the vaccinated flocks monitored long term remained high throughout life, flocks with high titers of both ELISAs in this survey must be vaccinated. Meanwhile, 34.3% (69 of 201) of flocks had high titers of DEWC-specific antibody alone. Because S.Enteritidis infection induces DEWC-specific but not SEP9-specific antibodies, DEWC-ELISA can be an effective monitoring tool for S.Enteritidis exposure rather than vaccination. These results suggest that vaccination programs in Japanese layer farms would be insufficient to control S.Enteritidis infection, and egg screening to detect specific antibodies would be valuable in obtaining the necessary information to control S.Enteritidis infection. Less