Serological response of patients with clinical typhoid

The techniques of immunoblotting and enzyme-linked immunosorbent assay (ELISA) were compared with the Widal test for examining the serum antibody response of patients with clinical typhoid. The Widal test detected antibodies in only four out of 16 patients. By ELISA and immunoblotting six patients were identified. With immunoblotting, patients' sera were found to contain antibodies binding to the 0=12 antigen of lipopolysaccharide (LPS), five of these sera also contained serum antibodies to H=d flagellar antigens. Serum antibodies to Salmonella typhi LPS, as detected by immunoblotting, correlated with high levels of antibodies to LPS as detected with a Salmonella enteritidis LPS ELISA. A rapid immunoblotting procedure was developed using S. enteritidis LPS and flagella prepared from S. meunchen, which could provide a serum test result within 1 day. This immunoblotting procedure might be a useful test to replace the Widal test as a diagnostic test for the serodiagnosis of typhoid.