EARLY DIAGNOSIS OF TYPHOID-FEVER BY AN ENZYME-IMMUNOASSAY USING SALMONELLA-TYPHI OUTER-MEMBRANE PROTEIN PREPARATIONS

An enzyme immunoassay (EIA) for detection of serum antibodies in patie nts with typhoid fever was developed using Salmonella typhi outer memb rane protein (OMP) preparations as antigen. Acute phase (first week) s era from adult typhoid fever patients were tested as well as sera from the following control groups: adult travellers with diarrhea caused b y enterotoxigenic Escherichia coli, children infected with Campylobact er jejuni, healthy Mexican adult blood donors, and adults with septice mia caused by other organisms. At a 1:3,125 serum dilution, the mean a bsorbance values were 1.41 in the typhoid fever patients, and 0.57, 0. 55, 0.51 and 0.52 in the respective control groups. Inhibition EIA stu dies using OMP preparations or lipopolysaccharide (LPS) as free antige n indicated that proteins can play an important role in the detection of antibodies in early typhoid fever. This EIA may be useful for the d iagnosis of typhoid fever since results were obtained within about fiv e hours and in an endemic area antibodies against Salmonella typhi OMP preparations appear early in the course of the disease.