An evaluation of purified Salmonella Typhi protein antigens for the serological diagnosis of acute typhoid fever

Summary Objectives The diagnosis of typhoid fever is a challenge. Aiming to develop a typhoid diagnostic we measured antibody responses against Salmonella Typhi ( S . Typhi) protein antigens and the Vi polysaccharide in a cohort of Bangladeshi febrile patients. Methods IgM against 12 purified antigens and the Vi polysaccharide was measured by ELISA in plasma from patients with confirmed typhoid fever (n = 32), other confirmed infections (n = 17), and healthy controls (n = 40). ELISAs with the most specific antigens were performed on plasma from 243 patients with undiagnosed febrile disease. Results IgM against the S . Typhi protein antigens correlated with each other (rho > 0.8), but not against Vi (rho 0.85, respectively. Applying a dynamic cut-off to patients with undiagnosed febrile disease suggested that 34–58% had an IgM response indicative of typhoid. Conclusions We evaluated the diagnostic potential of several S . Typhi antigens; our assays give good sensitivity and specificity, but require further assessment in differing patient populations.