Specific identification of Salmonella serogroup E antigen O3 by immunofluorescence and coagglutination with antiserum elicited by a synthetic trisaccharide-bovine serum albumin glycoconjugate.

Antiserum specific for Salmonella O3 antigen was raised by immunization of rabbits with an artificial glycoconjugate consisting of the synthetic trisaccharide beta-D- Manp (1----4)-alpha-L- Rhap (1----3)-alpha-D-Galp covalently linked to bovine serum albumin (beta- MRG -BSA). Enzyme immunoassays showed that only lipopolysaccharides extracted from Salmonella serogroup E (O3 antigen-containing) bacteria bound the antiserum. The usefulness of the beta- MRG -BSA antiserum for rapid and accurate identification of Salmonella isolates of serogroup E was shown by indirect immunofluorescence tests in which 50 Salmonella strains of serogroup E 1-4 were correctly identified from among 651 intestinal strains investigated. The finding that one strain of Citrobacter freundii was positive in immunofluorescence tests with this antiserum is readily explained by the known cross-reactivity between some C. freundii strains and Salmonella spp. strains of serogroup E. As expected, the specificity of the antiserum for the O3 antigen could further be demonstrated in coagglutination tests with staphylococci sensitized with beta- MRG -BSA antiserum.