We’ve all seen the signs in restaurant bathrooms stating “Employees must wash their hands before returning to work.” Shigellosis, a diarrheal disease caused by a toxic bacterium, is one of several infections that can be easily prevented with good hygiene and frequent hand washing.
Species Names: Shigella sonnei, Shigella flexneri, Shigella boydii, Shigella dysenteriae
Type of Microbe: Gram-negative bacteria
How it Spreads: Shigellosis is spread by person-to-person through the fecal-oral route (or ingestion of contaminated material after a bowel movement). It has been involved in several food-borne outbreaks through food handlers who used poor hygiene. It can also be spread through flies, swimming pools, and anal contact during sex.
Who’s at Risk? All people are at risk, but most cases are in small preschool-aged children, especially those who attend daycare centers. It is more common in the summer and fall seasons. Accordign to the Centers for Disease Control and Prevention, about 14,000 cases of shigellosis are reported annually in the United States, but the number of unreported cases is believed to bring the estimate up to 300,000 cases. In developing countries, the disease is endemic and can be fatal.
Symptoms: Acute symptoms include fever, severe lower abdominal pain and bloody diarrhea with mucous
Diagnosis: Gram-stain and culture of stool
Prognosis: Usually goes away within 5 to 7 days; hospitalization is rare.
Treatment: Usually not necessary, but antibiotics can shorten the illness. Anti-diarrheal drugs should be avoided, since they prevent the microbe from leaving the body and can make people sicker.
Prevention: Handwashing and good hygiene among adults and childre; use of clean water and sanitation systems. There is no vaccine available. It is important to follow hygiene techniques after changing kids' diapers and after using the bathroom.
How it Causes Disease: Ingestion of shigella results in invasion of the bacteria into the lining of the small intestine, where it multiplies. After 2 to 7 days, the bacteria invade the large intestine. Some species produce a “Shiga toxin” that causes inflammation and secretion of intestinal fluids. The toxin also damages the tissue lining of the large intestine and kidney.
Immunity: Once infected, it is unlikely to get infected with the same type of Shigella, due to the antibody immune response. However, infection by other types is still possible.
Complications: If the toxin damages the kidney, it may lead to hemolytic uremic syndrome. About 2% of people with Shigella flexneri develop “post-infectious arthritis”, with symptoms including joint pain, eye irritation, and painful urination.
Sources:
Shigella spp. FDA Bad Bug Book. Foodborne Pathogenic Microorganisms and Natural Toxins Handbook.
Shigellosis General Information. CDC DFBMD.
