Immunoenzymatic dot-blot test for the diagnosis of enteric fever caused by Salmonella typhi in an endemic area

To develop a quick, solid-phase immunoenzymatic test, dot blot, to diagnose typhoid fever by the detection of IgG and IgM antibodies against three Salmonella typhi antigens (lipopolysaccharide, crude and flagellar) and to compare the dot-blot test with an enzyme-linked immunosorbent assay (ELISA) using the same antigens and with the Widal agglutination test. Blood culture was used as the definitive test. All tests were used for the study of the sera from three groups of individuals: 33 patients suffering typhoid fever, diagnosed by isolation of S. typhi in blood culture; 35 patients with other enterobacterial infections documented by culture; and 156 asymptomatic volunteers, all residents of the same endemic region (Urabá, Colombia). The best diagnostic efficiency was obtained by detecting IgG against a flagellar antigen dot blot, giving a sensitivity and specificity of 88%. Widal and ELISA tests showed lower diagnostic efficiencies. The dot-blot test may be useful to diagnose typhoid fever in rural areas lacking technological resources with which to carry out blood cultures or ELISA tests. The visual reading makes this test practical and cheap for these regions.