How do Salmonella spp cause disease in people?
Usually, Salmonella spp are ingested. It is commonly accepted that at between 1 million to 1 billion bacteria are needed to cause infection although some investigators suggest some people may be infected by far fewer bacteria. Nevertheless, most data suggest food, water, or other sources of contamination contain large amounts of bacteria. Although human stomach acid can reduce and sometimes eliminate Salmonella spp, occasionally some bacteria get through to the intestine and then attach and penetrate the cells. Toxins produced by the bacteria can damage and kill the cells that line the intestines, which results in intestinal fluid loss (diarrhea). Some Salmonella can survive in cells of the immune system and can reach the bloodstream, causing blood infection (bacteremia). Other Salmonella spp can enter the gallbladder, leaving the affected patient a chronic carrier of the organisms. Salmonella can then be shed with the bile from the gallbladder into the feces and then may infect other
