Mechanism of interaction of Salmonella and Schistosoma species.

In endemic areas where Salmonella and Schistosoma species co-occur, several lines of evidence suggest a synergistic bacteria-parasite interaction that results in a protracted course for the salmonella infection that has proven difficult to diagnose and therapeutically remedy. In an in vitro system using a pilus-negative and a pilus-producing transductant strain of Salmonella typhimurium we show that pili are the ligands for bacterial adherence to the schistosome surface tegument. Antipili antibodies produced in rabbits against purified pili, purified and digested to monovalent (Fab) fragments, blocked the association of Salmonella sp. to the surface tegument of Schistosoma sp., further demonstrating that pili are the appendages necessary for bacteria-parasite surface interaction. The use of carbohydrates, lectins, and enzymes demonstrated that the bacteria-parasite surface interaction was specific, mediated by pili that specifically recognize and bind to mannose-like receptors, probably glycolipids, on the surface of the worms. We suggest that prolonged salmonellosis in schistosome-infected patients is due to an association of Salmonella sp. with the schistosome worms themselves and further that the schistosome worms provide a multiplication focus for these bacteria in the portal mesenteric system, with a persisting bacteremia following.