Shigellosis

Excerpt

Shigellosis is an acute diarrheal infection caused by an enteroinvasive gram-negative, facultative anaerobic bacillus of the genus Shigella. Shigellosis is common in developing countries, and transmission is via the fecal-oral route. Infection can occur via person-to-person contact or after ingesting contaminated food or water, especially in poor sanitation conditions. Recent reports reveal increased shigellae transmission via sexual contact, especially between men who have sex with men. Shigellosis can affect all persons across all age groups, but the very young, the elderly, and the immunocompromised are at significantly increased risk.

Shigellae are less susceptible to destruction by gastric acid when passing through the stomach; a small inoculum, as few as 10 to 100 organisms, is required to cause disease. After leaving the stomach, shigellae multiply in the small intestine and enter the colon. In the colon, this species secretes virulence factors that cause extreme inflammation and mediate enterotoxic effects to allow colonization and invasion of the colonic epithelium. Shigellae produce 3 enterotoxins, which cause watery or bloody diarrhea and infection-associated symptoms, such as tenesmus, malaise, and fever.

The average incubation period of shigellae is 1 to 4 days following ingestion of the inoculum. The main symptom of shigellosis is bloody and often mucoid diarrhea; abdominal pain and vomiting are common. Shigellosis is typically self-limited and resolves within 5 to 7 days. Antibiotics may be required to shorten the duration of illness or prevent complications, particularly in individuals at increased risk for severe disease and complications, such as hemolytic-uremic syndrome and postreactive arthritis. However, antibiotic resistance is rising within the genus, and extensively drug-resistant shigellae have been identified. Antimicrobial susceptibility testing is critical to ensure appropriate therapeutic selection.