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. | Characteristics | O Antigen | H Antigen |
|---|---|---|---|
| 1. | Types | Somatic Antigen | Flagellar antigen |
| 2. | Composition | Polysaccharide | Proteinaceous |
| 3. | Antibody formation | Rapid and Early | Rapid and Sustained |
| 4. | Level | Falls off quickly | Persists for longer periods |
| 5. | Production | Produces granular clumps. | Produces cottony, fluffy precipitates. |
| 6. | Observation | Round bottom Felix tube are used to see agglutination. | Conical bottom Dreyer’s tube are used to see agglutination. |
| 7. | Heat sensitivity | Somatic antigens are heat stable. | Flagellar antigens are heat-labile. |
| 8. | Alcohol sensitivity | Resistance to alcohol | Sensitive to alcohol |
| 9. | Extraction | Trichloro-acetic acid is used for extraction of O antigens. | Formaldehyde is used for extraction of H antigens. |
| 10. | Immunogenicity | Less immunogenic | Highly immunogenic |
| 11. | Antibody formation | Produces antibody formation with low titres. | Induces antibody formation with high titres. |