Vaccine potential of a nonflagellated virulence-plasmid cured, (fliD-, pSEV∆) mutant of Salmonella Enteritidis for chickens

The aim of these studies was to assess residual virulence and early protective capacity of a negatively markered live attenuated vaccine candidate Salmonella Enteritidis mutant against a highly virulent S. Enteritidis strain using a day old chicken model. Nonflagellated FliD negative mutants of Salmonella Enteritidis 11 (SE11) with and without the virulence-plasmid proved to be sufficiently attenuated (limited invasiveness in vitro/vivo) without reduced ability to colonise chicken gut. The early protective activity of a nonflagellated virulence plasmid cured (fliD-, pSEV∆) mutant against organ invasion, caecal colonisation and faecal shedding by the highly virulent challenge strain S. Enteritidis 147 NalR proved to be effective and safe. The innate and adaptive immunity was demonstrable during the first 4 weeks of life, and the serological response was clearly distinguishable from the response induced by the wild parental strain. In conclusion, we provided data for the first time about virulence plasmid cured nonflagellated mutant of S. Enteritidis to serve as a basis for development of a negatively markered potential live oral vaccine against virulent S. Enteritidis in chicken