The Shigella spp. bacteria are foodborne pathogenic microorganisms that are of particular concern to humans. The organisms include Shigella sonnei, Shigella boydii, Shigella flexneri, and Shigella dysenteriae. Shigella are gram-negative, nonmotile, nonsporeforming rod-shaped bacteria. The illness caused by Shigella (shigellosis) accounts for less than 10% of the reported outbreaks of foodborne illness in the United States. Shigella rarely occurs in animals and is principally a disease of humans but can also affect monkeys and chimpanzees. Infants, the elderly, and the infirm are susceptible to the severest symptoms of the disease, but of course all populations are susceptible to some degree. The organism is frequently found in water polluted with human feces. The disease is caused when virulent Shigella organisms attach to, and penetrate, epithelial cells of the intestinal mucosa. After invasion, they multiply intracellularly, and spread to contiguous epithelial cells resulting in tissue destruction. Because the organisms penetrate the gastrointestinal tract diagnosis of the disease is done by serological identification of a culture isolated from stool sample. One interesting fact is that some strains produce enterotoxin and Shiga toxin, which is very much like the verotoxin of Escherichia coli. Shigellosis or bacillary dysentery symptoms include abdominal pain, cramps, diarrhea, fever, vomiting, blood, pus, or mucus in stools, and tenesmus. Symptoms have an onset time of 12 to 50 hours and once they appear can be very uncomfortable and in some cases fatal. Some infections are associated with mucosal ulceration, rectal bleeding, drastic dehydration; fatality may be as high as 10-15% with some strains. Reiter's disease, reactive arthritis, and hemolytic uremic syndrome are possible sequelae that have been reported in the aftermath of shigellosis. Since the disease is found most often in fecal contaminated water there are certain foods that are more susceptible to invasion. These include: salads (potato, tuna, shrimp, macaroni, and chicken), raw vegetables, milk and dairy products, and poultry. Contamination of these foods is usually through the fecal-oral route. Fecal contaminated water and unsanitary handling by food handlers are the most common causes of contamination. There are an estimated 300,000 cases of shigellosis annually in the U.S. It is not known how many cases are attributed to food, but given the low infectious dose, it is probably substantial. In the late 1980s there was an outbreak of cases in which innovative public health control measures were used. During that time the reported isolation rate of Shigella in the United States increased from 5.4 to 10.1 isolates per 100,000 persons. There were 17 cases of diarrhea disease cause by S. dysenteriae, and outbreak of multiple resistant S. sonnei gastroenteritis and another S. sonnei species was isolated from 15 children at a daycare center. The largest outbreak of foodborne shigellosis occurred in Midland- Odessa, Texas, involving more than 5,000 people. Lettuce was chopped and prepared in a local Mexican restaurant. FDA research subsequently showed that S. sonnei, the isolate from the lettuce could survive in chopped lettuce under refrigeration, and the lettuce remained fresh and appeared to be quite edible. Many of the outbreaks dealing with food have found to have the isolate, S. sonnei this shows that this strain is clearly the leading cause of shigellosis from food.
In conclusion, shigellosis is a foodborne disease that can cause poisoning of your gastrointestinal tract and in some cases lead to serious complications. To decrease your risk of shigellosis, beware of fresh vegetables from salad bars and wash your hands after you do #2!
*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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