This experiment was conducted to study the immune response of
chickens to S. enteritidis infection or different vaccines either by micro
titer serum plate agglutination test or by immunoblot test. Different
groups were included: chickens vaccinated by live S. enteritidis
vaccine (s/c), chickens vaccinated by locally prepared or commercial
S. enteritidis bacterins intramuscularly (i.m), and chickens infected
orally or intramuscularly by a pathogenic strain of S. enteritidis. Also,
the effect of antibiotic treatment on the serological response in live
vaccine or infection groups was studied. Agglutination test could
detect 100% positive reactors in the first week post vaccination and
challenge. The results revealed that the highest serum micro plate
agglutination titer was Log10 3.8 obtained by locally prepared
bacterin and also obtained by intramuscular infection with pathogenic
S. enteritidis. Immunoblotting could detect reacting sera only in the
second week post vaccination or infection. Antibiotic (sulphatrimethoprime)
treatment decreased the number of reacting bands in
the immunoblot by 1-3 bands less than those infected and not treated
with antibiotics. Intramuscularly infected chicks showed 1-2 bands
more than orally infected chicks. Live pathogenic bacteria injected
i.m. produced higher geometric mean titers and more bands in the
immunoblot than the bacterin prepared from the same strain and
injected via the same route.