Serodiagnosis of typhoid fever by enzyme-linked immunosorbent assay determination of anti-Salmonella typhi lipopolysaccharide antibodies

Serum samples from 22 patients with proven typhoid fever, 60 febrile nontyphoidal patients, and 120 healthy subjects were tested for immunoglobulin A (IgA), IgG, and IgM anti-Salmonella typhi lipopolysaccharide antibodies by an enzyme-linked immunosorbent assay. The levels of all three classes of immunoglobulin anti-lipopolysaccharide were higher in typhoid patients than in controls; the test for IgM anti-lipopolysaccharide gave the best discrimination between typhoid and nontyphoidal sera. The absorbance values obtained with the enzyme-linked immunosorbent assay for IgM anti-lipopolysaccharide were highly correlated to the titers of anti-O agglutinins. However, the enzyme-linked immunosorbent assay was much more specific than the Widal test, and hence it could be a useful tool for the serological diagnosis of typhoid fever with a single blood sample.