Enzyme-linked immunosorbent assay with a Salmonella enteritidis antigen for differentiating infected from vaccinated poultry

Outer membrane protein BamA-based ELISA differentiates Salmonella-vaccinated chickens from naturally infected chickens

Salmonella often causes subclinical infection in chickens, but antibody tests can find infected individuals and control the spread of infection. In this study, the S. Typhimurium-specific outer membrane, β-barrel assembly machinery protein A (BamA), was overexpressed in Escherichia coli and purified as a coating antigen to develop a BamA-based enzyme-linked immuno sorbent assay for detecting Salmonella infection. The presence of anti-BamA IgG was detected in the sera of infected BALB/c mice, but not in that of heat-killed Salmonella-vaccinated mice. The assay was validated using White Leghorn chickens and showed similar results. The detection of BamA antibodies in the sera can differentiate infected chickens from vaccinated chickens. This assay will be useful for monitoring Salmonella infection in chickens and possibly in other animals.

Mapping B-cell responses to Salmonella enterica serovars Typhimurium and Enteritidis in chickens for the discrimination of infected from vaccinated animals

Serological surveillance and vaccination are important strategies for controlling infectious diseases of food production animals. However, the compatibility of these strategies is limited by a lack of assays capable of differentiating infected from vaccinated animals (DIVA tests) for established killed or attenuated vaccines. Here, we used next generation phage-display (NGPD) and a 2-proportion Z score analysis to identify peptides that were preferentially bound by IgY from chickens infected with Salmonella Typhimurium or S. Enteritidis compared to IgY from vaccinates, for both an attenuated and an inactivated commercial vaccine. Peptides that were highly enriched against IgY from at least 4 out of 10 infected chickens were selected: 18 and 12 peptides for the killed and attenuated vaccines, respectively. The ten most discriminatory peptides for each vaccine were identified in an ELISA using a training set of IgY samples. These peptides were then used in multi-peptide assays that, when analysing a wider set of samples from infected and vaccinated animals, diagnosed infection with 100% sensitivity and specificity. The data describes a method for the development of DIVA assays for conventional attenuated and killed vaccines.

Incidence of Salmonella infection in healthy dogs in Gifu Prefecture, Japan

A total of 1,013 feces samples and 8 mesenteric lymphonodus samples obtained from apparently healthy dogs were examined for the incidence of salmonella infection. One strain of S. typhimurium (ST) was isolated from feces of one dog, and S. enteritidis (SE) was isolated from the mesenteric lymphonodus of one dog. Sera obtained from 330 apparently healthy dogs were examined for Salmonella antibodies using an ELISA with heated whole cells of SE and ST. Fifty-one of the 330 serum samples were considered to be positive for salmonella antibodies, including 12 which were SE-positive and 39 which were ST-positive. These results indicate that dogs cause possible environmental problems as Salmonella carriers.