Gram Negative Bacilli
In salmonella infection:
|A||Flagellar antigen forms chalky granular clumps|
|B||Somatic antigen is a protein|
|C||Absence of Vi antibody indicate poor prognosis|
|D||Serological classification is by craiges scheme|
a. H (flagellar) antigen is proteinaceous antigen and forms fluffy agglutination in Widal test.
b. (somatic antigen) is a polysaccharide antigen and produces chalky or granular agglutination in Widal test. Identification of Salmonella is based on Kauffman and White scheme who used the O antigen and the H antigen.
c. Antibodies to Vi antigen are thought to be protective, therefore absence of these is considered as poor prognosis.
Salmonella typhi antigens
Heat labile, strongly immunogenic
Antibody to H- Ag appears 1 st & persists
Agglutination with antiserum is fluffy- in Dreyer's tube
heat stable ,Virulence factor
somatic cell wall Ag
more in diseased person
used for classification
agglutination with antiserum is compact and disc like- in Felix tube
Used in epidemiological typing by use of Vi phages. Is Capsular Ag
absence of Ab to this Ag indicates poor prognosis
prevents the agglutination of S. Typhi with "O" Antiserum
used for carrier state detection