DETECTION OF ANTIBODIES TO SALMONELLA-ENTERITIDIS IN SERA AND YOLKS FROM EXPERIMENTALLY AND NATURALLY INFECTED CHICKENS

An indirect enzyme-linked immunosorbent assay (ELISA) based on the lip opolysaccharide (LPS) of Salmonella enteritidis phage type 4, was deve loped for the detection of antibodies to salmonella, Sera and yolks fr om chickens infected experimentally with S enteritidis showed strong p ositive reactions, Cross-reactions occurred with sera from chickens in oculated with S typhimurium or S gallinarum. Cross-reactions were weak with sera from chickens infected with five strains of other Enterobac teriaceae. The ELISA was tested with sera and yolks from commercial po ultry flocks which were bacteriologically negative for salmonella or i nfected with salmonella serotypes belonging to serogroup D or to other serogroups. The serological reactions were strong in most flocks infe cted with S enteritidis and were weaker in flocks infected with S typh imurium. In some flocks infected with these serotypes no antibodies we re detected, The correct setting of the cut-off value of the optical d ensity in the ELISA makes it possible to discriminate between chickens which are infected with S enteritidis and chickens which are not infe cted with S enteritidis.