In America, there are approximately two million cases of Salmonella infections every year, according to Jerry Trier, M.D., professor of medicine emeritus at Harvard Medical School, in "Current Diagnosis & Treatment: Gastroenterology, Hepatology & Endoscopy." Most of these infections are due to Salmonella typhimurium and Salmonella enteritidis. These organisms cause acute enterocolitis, or the inflammation of the small and large intestines.
Transmission of Disease
Salmonella typhimurium is a bacterium. People develop an infection when they eat contaminated food that has not been properly washed or cooked enough. S. typhimurium especially contaminates meat and chicken, but it also contaminates dairy products, eggs, vegetables, peanut butter and water. Some people may even develop an infection from pets such as reptiles. In December 2009, the Centers for Disease Control and Prevention reported an outbreak in 31 states which they determined was from contact with water frogs.
Risk Factors
In "Current Diagnosis & Treatment: Gastroenterology, Hepatology, & Endoscopy," Dr. Trier explains that S. typhimurium is sensitive to acid. Because of the normal amount of acid in the stomach, it takes more Salmonella organisms to cause an infection than Shigella. Shigella is another bacterium that causes intestinal infections, but it is not sensitive to acid. A small amount of Shigella can cause disease. Since S. typhimurium is sensitive to acid, people who are at risk for developing its disease are people who have less stomach acid because of medication, disease or surgery. The very young and the elderly, those with cancer and those with an impaired immune system are also at risk.
Development of Disease
Approximately 100 Shigella organisms can cause disease. It takes at least 100,000 S. typhimurium organisms because of their sensitivity to stomach acid, according to Warren Levinson, M.D., Ph.D., professor of microbiology at the University of California in "Review of Medical Microbiology and Immunology." If there are enough of them, they can migrate from the stomach and invade the small and large intestines, causing acute enterocolitis. This is the inflammation of both intestines. Neutrophils respond to the infection; they are a type of white blood cell that has the job of fighting bacteria. Most of the time, they can limit the S. typhimurium infection to the intestines and nearby lymph nodes. The neutrophils prevent the bacteria from reaching the bloodstream and spreading throughout the body.
Symptoms
Twelve to 48 hours after eating contaminated food or drinking contaminated water, people will have nausea and vomiting. This develops to abdominal pain and diarrhea. The diarrhea can be mild or it may be severe. It may or may not be bloody. Most of the time, however, it is not bloody, and the acute enterocolitis lasts for just a few days. Then it goes away on its own. The very young and the elderly may need medical care, per Dr. Levinson in "Review of Medical Microbiology and Immunology."
References
- Centers for Disease Control and Prevention: Salmonella Typhimurium Infections Associated with Contact with Water Frogs
- "Current Diagnosis & Treatment: Gastroenterology, Hepatology, & Endoscopy"; Norton Greenberger, M.D.; 2009
- "Review of Medical Microbiology and Immunology"; Warren Levinson, M.D., Ph.D.; 2008
