Widal test is used for the diagnosis of

Widal test is bacterial agglutination test, originally introduced by Widal for diagnosis of typhoid fever. Widal test is based upon antigen antibody serological interactions. Typhoid or enteric fever is caused by a Gram-negative bacterium Salmonella commonly found in human intestine. Infection of typhoid bacteria stimulates the production of immuno-specific agglutinins, which are released in blood plasma.