Salmonella Typhi/Paratyphi Antigen Rapid Test

Background of Clinical Indications

Typhoid fever is a life-threatening illness caused by the bacterium Salmonella typhus, and was observed by Eberth (1880) in the mesenteric nodes and spleen of fatal cases of typhoid fever. It is common in developing countries where it affects about 12.5 million persons annually. The infection is acquired typically by ingestion. On reaching the gut, the bacilli attach themselves to the epithelial cells of the intestinal villi and penetrate the lamina and submucosa. They are then phagocytosed there by polymorphs and mesenteric lymph nodes, where they multiply and, via the thoracic duct, enter the blood stream. A transient bacteremia follows, during which the bacilli are seeded in the liver, gall bladder, spleen, bone marrow, lymph nodes, and kidneys, where further multiplication takes place. Towards the end of the incubation period, there occurs a massive bacteremia from these sites, heralding the onset of the clinical symptoms. Serovar Paratyphi A is the second most prevalent cause of Typhoid. Paratyphi and S.Typhi cause a similar illness, with relapsing fever. The diagnosis of Typhoid and Paratyphoid consists of isolation of the bacilli and the demonstration of antibodies. The isolation of the bacilli is very time consuming and antibody detection is not very specific. The Salmonella Typhi/Paratyphi Antigen Rapid Test employs a combination of monoclonal antibody/colloidal gold dye conjugate and a polyclonal antibody to qualitatively detect S. Typhi and/or Paratyphi antigens in human fecal specimens.