Application and Usefulness of Enzyme Immunoassay for Diagnosis of Salmonella Typhimurium Infection

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Abstract
An enzyme immunoassay for serogroup specific immunological diagnosis of Salmonella infections was developed. Antigens representing Salmonella O antigens 4 (serogroup B) and 9 (serogroup D) were prepared by periodate oxidation of phenol-water extracted lipopolysaccharides from S. typhimurium and S. enteritidis, respectively. Applied for seroepidemiological studies of S. typhimurium infections [human] such chemically modified antigens showed a superior specificity compared to native lipopolysaccharides. The antibody titers against O antigen 4 measured by the enzyme-linked immunosorbent assay (ELISA) were detectable during the 2nd wk and increased during the first 3-4 wk of S. typhimurium infection. High titers persisted for at least 2-3 mo. and in some cases for more than 3 yr. For reliable serodiagnosis a significant increase of the titer between acute and convalescent samples is necessary. Determination of ratio between Ig[immunoglobulin]G and IgM antibody titers against the pathogen may be used on single serum samples to indicate whether the observed antibody titer is of recent or longstanding origin.