Shigella as a Pathogen
Shigellosis, or bacillary dysentery, as it is commonly known, is caused by bacteria of the genus Shigella (S. dysenteriae, S. flexneri, S. boydii and S. sonnei). The normal habitat for Shigellae is the intestinal tract of humans and other primates. They are rarely found in other animals. The main source of Shigellae involved in outbreaks is asymptomatic carriers or persons recovering from disease. Shigellae may persist in the intestinal tract for month.
Symptoms of shigellosis, after an incubation period of 1-7 days (usually less than 4 days), include diarrhea, abdominal pain, fever, and vomiting. The severity of the disease may vary from very mild to severe diarrhea with bloody stools, mucus secretion, and dehydration. Generally foodborne shigellosis is characterized by a high attack rate common source epidemiology, and short incubation periods of 7 – 36 hours. Symptoms usually persist for 3 – 14 days. Frequently, an asymptomatic carrier state may develop during convalescence, lasting from a few days to several months. Human volunteer studies indicate that ingestion of as few as 1 – 100 organisms can induce illness.
The disease is caused by invasion of the intestinal mucosa. An enterotoxin, classically referred to a Shiga toxin, may be produced by S. dysenteriae and possibly by S. flexneri.
Shigella as a Pathogen
