Further observations on the serological response to experimental Salmonella typhimurium in chickens measured by ELISA

Abstract

SUMMARYAn indirect ELISA developed for the serological detection of Salmonella typhimurium in chickens using lipopolysaccharide as detecting antigen has been evaluated further in experimental infections. Following oral infection of 24-weekold laying hens with an invasive strain of S. typhimurium, high titres of specific circulating IgG were induced which were maintained for 20 weeks. Similar IgG titres were found in egg yolk. When 4-day-old chickens were infected high antibody titres persisted for 45 weeks. Chickens inoculated orally or intramuscularly with different numbers of S. typhimurium organisms showed graded serum IgG responses to LPS. The IgG titres in experimentally infected in-bred lines of chickens which showed greater genetic resistance to salmonella infection were significantly lower than those found in more susceptible lines. Oral and intramuscular infection with 18 different types of enterobacteria, including avian pathogenic E. coli, Citrobacter spp., Klebsiella spp., Proteus spp. and citrobacterlike organisms possessing some salmonella LPS (none possessed the 0-4 antigen) and flagella antigens, did not induce S. typhimurium LPS-specific IgG responses. Chickens infected orally with rough or non-flagellate mutants of S. typhimurium did not induce high titres of LPS or flagella-specific IgG respectively. Sera obtained from S. typhimurium-infected chickens showed much higher titres against S. typhimurium LPS than with those antigens from other serotypes, including S. enteritidis.

ELISAs and the serological analysis of salmonella infections in poultry: a review

“…The IgG titre obtained is, to some extent, dose dependent and is related to the extent of faecal excretion but not necessarily so for individual birds [21,28]. This again emphasizes the value of the ELISA and presumably of other quantitative serological tests, as a flock rather than an individual bird test, since the intermediate IgG titres obtained after infection with a small number of salmonella organisms may be difficult to interpret.…”

“…LPS is the most frequently used discriminating detecting antigen. Sera obtained from chickens infected either with S. typhimurium [28] or with S. gallinarum [27] yielded much higher titres with homologous rather than heterologous LPS as detecting antigen. LPS from serogroups B, C1 and C2, D and 0-35 were tested.…”

“…Differentiation between infections caused by S. enteritidis, S. gallinarum and its biovar pullorum using different LPS preparations as coating antigens has also been claimed [35] but there have been no further reports of this. However, varying degrees of cross reactions between group B and D LPS have been demonstrated with sera from chickens infected with S. typhimurium [20,27,28]. This cross reaction has also been demonstrated by immunoblotting [18].…”

“…High IgG titres persist for many weeks following infection with S. enteritidis [23,26], S. gallinarum [27] and S. typhimurium [28] respectively. In the last case high titres were still present 45 weeks after infection.…”

“…It has been applied to S. enteritidis, typhimurium and gallinarum [24,27,28,33,34]. In chickens experimentally infected with either S. typhimuriurn or S. gallinaruam, specific-IgG titres in egg yolk were found (after an initial lag) to be very similar to serum titres [27,28]. LPS is the most frequently used discriminating detecting antigen.…”