Agglutination in Vi grouping serum is a diagnostic feature used to identify which serovar of Salmonella?

Agglutination in Vi grouping serum is a diagnostic feature used to identify which serovar of Salmonella?

• A. Salmonella enteritidis
• B. Salmonella typhi
• C. Salmonella paratyphi
• D. Salmonella choleraesuis

Answer: (B)

Agglutination with Vi grouping serum relies on antibodies recognizing the Vi capsule, a polysaccharide capsule that is characteristic of Salmonella Typhi. When you mix anti-Vi serum with a Salmonella isolate, only strains that express the Vi antigen will clump together, so a positive Vi agglutination test points to Typhi. The other serovars listed generally lack this Vi capsule, so they do not react with anti-Vi serum. That makes Vi agglutination a diagnostic clue specifically for identifying Salmonella Typhi.

Agglutination with Vi grouping serum relies on antibodies recognizing the Vi capsule, a polysaccharide capsule that is characteristic of Salmonella Typhi. When you mix anti-Vi serum with a Salmonella isolate, only strains that express the Vi antigen will clump together, so a positive Vi agglutination test points to Typhi. The other serovars listed generally lack this Vi capsule, so they do not react with anti-Vi serum. That makes Vi agglutination a diagnostic clue specifically for identifying Salmonella Typhi.