Identification of salmonellae of serogroup C1 by immunofluorescence and co-agglutination with antiserum against an oligosaccharide-protein conjugate.

Antiserum specific for salmonella O7 antigen raised by immunisation of rabbits with an artificial conjugate consisting of oligosaccharide and bovine serum albumin (Os-BSA). The oligosaccharide was a pentasaccharide isolated after cleavage of the O antigen polysaccharide chain of Salmonella thompson (O antigen 6, 7) with endo-glycanase from bacteriophage 14. The usefulness of the S. thompson Os-BSA antiserum for rapid and accurate identification of isolates of Salmonella of serogroup C1 (O6, 7) was shown by indirect immunofluorescence tests in which 77 strains of Salmonella of serogroup C1 were correctly identified from among 848 intestinal strains investigated. The finding that three strains of Escherichia coli and most strains of Candida were also positive in immunofluorescence tests with this antiserum is readily explained by the known structural similarities among the antigenic determinants of E. coli, Candida and Salmonella of serogroup C1. The specificity of the antiserum for the O7 antigen determinant was further demonstrated in enzyme-linked immunosorbent assay tests and in co-agglutination tests with staphylococci sensitised with S. thompson Os-BSA antiserum.