How Do Salmonella spp Cause Disease(s)?
The majority of Salmonella spp are ingested with food or water. In people with normal gastrointestinal tracts and immune systems, researchers have estimated that about 1 million to 1 billion S. spp need to be ingested to cause infection, because normal human stomach acid can kill large numbers of these bacteria. If some bacteria reach the intestine, the organisms can attach to intestinal cells where S. spp toxins (cytotoxin and enterotoxin) can damage and kill cells. The intestinal cell damage results in the inability of the body to normally retain and adsorb fluids, so diarrhea results. In some people, the diarrhea can cause serious dehydration. However, the majority of S. spp infections are then eventually eliminated by the person’s immune defenses. Some S. spp are not eliminated; these bacteria survive the initial immune response by living inside cells (macrophages) of the immune system. The bacteria can sometimes spread to the blood (bacteremia). Some S. spp (for example, S. typhi)
