A study on the usefulness of counter immuno-electrophoresis for the detection of Salmonella typhi antigen in the sera of suspected cases of enteric fever.

Counter immuno-electrophoresis (CIE) was used to detect the presence of Salmonella typhi antigen and antibodies in the sera of 123 suspected cases of enteric fever. Of these, 68 had been incompletely treated with various antibiotics before establishing the diagnosis. The sera of 31 (25%) of the 123 cases showed the presence of S. typhi antigen. Blood culture was positive for S. typhi in only one case. Antigen could be demonstrated in sera of patients with fever ranging from two to ten days. Antigen could also be demonstrated after ten days in sera of patients who had taken some antibiotics. There is no apparent relationship between the presence of antigen and antibodies in the sera, and no apparent relationship between the CIE antibody and Widal antibody titres.