Difference between O Antigen and H Antigen

The antigen used to define serological test of Salmonella include Somatic O antigen, Flagellar H antigen and Vi antigen (Capsular antigen).

Some of the differences between O Antigen and H Antigen are as follows:

S.N.CharacteristicsO AntigenH Antigen
1.TypesSomatic AntigenFlagellar antigen
2.CompositionPolysaccharideProteinaceous
3.Antibody formationRapid and EarlyRapid and Sustained
4.LevelFalls off quicklyPersists for longer periods
5.ProductionProduces granular clumps.Produces cottony, fluffy precipitates.
6.ObservationRound bottom Felix tube are used to see agglutination.Conical bottom Dreyer’s tube are used to see agglutination.
7.Heat sensitivitySomatic antigens are heat stable.Flagellar antigens are heat-labile.
8.Alcohol sensitivityResistance to alcoholSensitive to alcohol
9.ExtractionTrichloro-acetic acid is used for extraction of O antigens.Formaldehyde is used for extraction of H antigens.
10.ImmunogenicityLess immunogenicHighly immunogenic
11.Antibody formationProduces antibody formation with low titres.Induces antibody formation with high titres.

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