Salmonella Grouping Antisera are used in qualitative slide agglutination tests for the serological differentiation of Salmonella. Using these antisera, Salmonella isolates may be classified into groups A, B, C1, C2, D and E according to their somatic (O) antigens. The Salmonella O Polyvalent antiserum is used for screening in conjunction with biochemical tests. The Salmonella Vi antiserum detects the Vi antigen, a heat-sensitive envelope antigen usually found in fresh isolates of S. typhi and S. paratyphi C.