Salmonella enterica can be considered as one of the most important causes of foodpoisoning with poultry thought to be the main source. Although S. Typhimurium, S.
Enteritidis and the vast majority of other Salmonella serovars generally produce little
systemic disease in adult chickens, they are able to colonize the alimentary tract of poultry.
The two caeca are the main sites of the colonization of Salmonellae in chickens, and the
bacteria can be easily harvested from the caeca for analysis. Bacterial proteins analysed
utilizing SDS-PAGE showed differences between in vitro and in vivo that out of about 40
protein bands of in vitro preparation only a few (3-5) bands can be visualized from in vivo
preparations. We suggested that some avian proteases might be responsible. Accordingly,
and to investigate the hypothesis that bacterial-precipitated protein harvested from
chickens is thought to be more protective than bacteria grown in broth culture, the
immunogenicity of protein-precipitated vaccines harvested from chicken intestine and those
from broth culture (in vitro), were compared using bacterial proteins as an orally inoculated
vaccine candidate in chicken. The results demonstrated that the in vitro sonicated proteins
obtained from a nutrient broth culture had a much better protective vaccine effect than the
in vivo sonicated proteins preparations harvested from bacteria grown in chickens.