Widal reaction

Wi·dal reaction also Wi·dal's reaction vē-'däl(z)- n a specific reaction consisting in agglutination of typhoid bacilli or other salmonellas when mixed with serum from a patient having typhoid fever or other salmonella infection and constituting a test for the disease

Wi·dal vē-däl Georges-Fernand-Isidore (1862-1929)

French physician and bacteriologist. Widal held a professorship of pathology and internal medicine at the University of Paris. In 1896 he developed the Widal reaction, a procedure for diagnosing typhoid fever based on the fact that antibodies in the blood of an infected individual cause the bacteria to bind together into clumps. In 1906 he recognized that the retention of sodium chloride was a feature found in cases of nephritis and cardiac edema, and he recommended salt deprivation as part of the treatment for both diseases.

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an agglutination test for the presence of antibodies against the Salmonella organisms that cause typhoid fever. It is thus a method of diagnosing the presence of the disease in a patient and also a means of identifying the organisms in infected material.

G. F. I. Widal (1862-1929), French physician

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see under test.