system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Agglutination with 'O' antigen of S. typhi is inhibited by :-
assistant
The correct answer is  Agglutination with 'O' antigen of S. typhi is inhibited by Vi antigen. Vi antigen: Surface polysaccharide envelope or capsular antigen covering the O antigen. Prevents its agglutination with O antiserum. Phage typing of S. typhi can be done by using Vi specific bacteriophages. Used for vaccination.