SEROLOGY AND WIDAL AGGLUTINATION TEST
Serology test are usually dependent on Antigen-Antibody reaction. This reaction occurs when antigen combines with the antibody to give a reaction. If a patient is infected with a particular organism, the body forms antibody against the infecting agent (antigen) so when an antigen reacts with serum of an individual suspected to have a certain disease, there would be a reaction as long as the antibody is specific for that specific antigen.
WIDAL AGGLUTINATION TEST
Widal agglutination test is done using Febrile Antigen. Febrile antigens are stained bacterial antigen suspensions for the identification and quantitative determination of specific antibodies in human serum, following infection with certain Salmonellae, Rickettsiae and Brucellae pathogens.
Principle of the Method
Febrile antigens are suitable for use with both the rapid slide and tube agglutination tests using human serum.
These stained bacterial antigen suspensions are bacteria killed and stained to enhance the reading of the agglutination reaction. The blue stained antigens are specific to somatic ‘O’ antigens, while the red stained antigen are specific to flagella ‘H’antigens.
The ‘O’antigen which includes
Salmonella O antigen, group A
Salmonella O antigen, group B
Salmonella O antigen, group C
Salmonella O antigen, group D (Typhi O)
The ‘H’antigens are;
Salmonella H Antigen, antigen a
Salmonella H Antigen, antigen b
Salmonella H Antigen, antigen c
Salmonella H Antigen, antigen d (Typhi H)
- Bring the reagent and samples to room temperature.
- Resuspend the antigen vial gently, aspirate dropper several times to obtain a thorough mixture.
- Using a suitable pipette, place a drop of serum into a row of 3cm diameter circles, using a white tile.
- Add one drop of appropriate undiluted antigen suspension to each serum aliquot.
- Mix well using a stirring stick, starting with the mixture first to the last, spreading the contents over the entire area of the circle.
- Slowly rotate the tiles on the sedstainer.
- Read agglutination after 1 minute.