Bacterial Immunoserology

Determination of baseline Widal titre among apparently healthy population in Dehradun City

“…The O antigen is the somatic antigen and antibodies against the O antigen are predominantly IgM which rise early in the illness and disappear early. The H antigens are flagellar antigens of Salmonella typhi, paratyphi A and paratyphi B. Antibodies to H antigens are both IgM and IgG which rise late in the illness and persist for a longer time [4,6]. In endemic areas, baseline anti O and anti H antibodies are present in the population owing to repeated subclinical infections with Salmonella Typhi / Paratyphi [6].…”

“…Classically four-fold rise of antibody in paired sera is considered diagnostic of typhoid fever [4]. But paired sera are often difficult to obtain and specific chemotherapy has to be instituted on the basis of a single Widal test [5].…”