Serodiagnosis of typhoid fever in paediatric patients by anti-LPS ELISA

Abstract

Enzyme-linked immunosorbent assay (ELISA) and immunoblot analysis showed that up to 50% of the anti-typhoid antibody in sera from blood culture positive paediatric typhoid fever patients is directed against lipopolysaccharide (LPS) antigen. Anti-Salmonella typhi LPS ELISA was therefore compared to Widal agglutination for serodiagnosis of typhoid fever in paediatric patients. Sera from 38 paediatric control individuals were ELISA negative for anti-S. typhi LPS IgG; all but 2 of these specimens were negative for anti-S. typhi LPS IgM. Paediatric patients hospitalized with signs and symptoms of typhoid fever were separated into 4 groups and tested by ELISA with the following results: 46 patients negative by both culture and Widal agglutination tests, 48% positive for anti-S. typhi LPS IgG and 35% for anti-S. typhi LPS IgM; 22 negative by culture but with positive Widal titres, 82% and 68% positive respectively; 28 culture positive for S. typhi, 93% and 82% respectively; and 12 culture positive for Salmonella other than S. typhi, 92% and 92% respectively. These data suggest that anti-S. typhi LPS ELISA is a suitable assay for diagnosis of typhoid fever in children.