In salmonella infection, true statement is:

Absence of Vi antibody indicate poor prognosis in salmonella infection is the true statement among the options given above. Option 1 Option 2 Somatic antigen (O Ag): Pa of cell wall lipopolysaccharide (LPS). Flagellar antigen (H Ag): Made-up of proteins: flagellin, confers motility. Option 3 The complete absence of the Vi antibody in a proven case of typhoid fever indicates poor prognosis Option 4 Phase variation: Conversion of isolates from one phase to another is achieved by using Craigie's tube method. Note: Vi Antibodies are not seen in normal population.