Indirect antigen-trap ELISAs using polyclonal antisera for detection of group B and D Salmonellas in chickens

Indirect antigen-trap ELISAs able to detect Salmonella typhimurium and S. enteritidis are described. Their limits of sensitivity were about 10(7) organisms in nutrient broth culture. With the ELISA developed for S. typhimurium, 76 of 77 strains gave optical density (OD) readings of 1.06 to 1.40. Three other serotypes from group B in the Kaufmann-White scheme gave high values: S. saintpaul produced an OD of 1.40, S. schwarzengrund 0.93 and S. derby 0.88. Twenty other serotypes all produced OD values of 0.39 to 0.66. Four Citrobacter strains and an E. coli produced lower values. With the S. enteritidis ELISA, seven strains of this serotype produced OD values of 1.13 to 1.23 and 13 other serotypes gave OD values of 0.14 to 0.87. There was good correlation between the ELISA and bacteriological culture after examining selenite broth cultures of cloacal swabs taken from experimentally infected chickens. A few samples were positive by ELISA and negative by culture and vice versa. Similar results were obtained from cloacal swabs taken from a commercial flock known to be infected with S. typhimurium. Much closer correlation existed between the two methods for identifying artificially contaminated eggs or for spleens taken from experimentally infected birds.