• Shigella are a moderately-sized, non-motile, Gram-negative bacilli.
• Facultative anaerobes (def).
• There are 4 species of Shigella: S. dysenteriae, S. flexneri, S. boydii, and S. sonnei.

Habitat

• The intestinal tract of infected humans.

Source

• Humans are the only reservoir for Shigella. Transmitted by the fecal-oral route.

Epidemiology

• Over 23,600 cases of shigellosis were reported in the U.S. in 1998 but most cases are not reported. An estimated 450,000 are thought to occur each year in the U.S.
• The most common cause of shigellosis in developed countries is S. flexneri.
• 70% of all Shigella infections occur in children under the age of 15.

Clinical Disease

• Symptoms of shigellosis include diarrhea, bloody stool, abdominal cramps, and fever. The incubation period is 1-3 days.
• Initial profuse watery diarrhea typically appears first as a result of enterotoxin. Within 1-2 days this progresses to Abdominal cramps and tenesmus (def), with or without bloody stool. Classic shigellosis presents itself as lower abdominal cramps and stool abundant with blood and pus develops as the Shigella invade the mucosa of the colon.

FromShigella Infection, by Walid Abuhammour, MD, FAAP, Associate Professor of Pediatrics, Michigan State University; Director of Pediatric Infectious Disease, Department of Pediatrics, Hurley Medical Center and Ilyas Burny, MD, Staff Physician, Department of Pediatrics, Hurley Medical Center.