The Vi antigen of Salmonella Typhi is best applied in public health practice for which purpose?

• A Differentiating Typhi from Paratyphi A biochemically
• B Screening populations to identify chronic carriers of S. Typhi ✓
• C Confirming the diagnosis of acute typhoid in the first week
• D Typing strains for epidemiological tracking by phage susceptibility

Explanation

Vi antigen is a surface capsular polysaccharide expressed by virulent strains of S. Typhi. Most chronic carriers develop detectable serum anti-Vi antibodies, so Vi agglutination serves as a practical screening tool to identify carriers among food handlers, with confirmation by repeated stool or bile cultures. Acute diagnosis relies on blood culture early and Widal testing later, and epidemiological typing uses phage typing or molecular methods rather than Vi.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.