Shigellosis

Excerpt

Shigellosis is an acute diarrheal infection caused by an enteroinvasive gram-negative, facultative anaerobic bacillus of the genus Shigella (see Image. Shigellosis). Shigellosis is common in developing countries and is transmitted via the fecal-oral route. In high-income countries, reports reveal that, in addition to young children, men who have sex with men are at risk for Shigella outbreaks via sexual contact. Shigellosis can affect all persons across all age groups, but the very young, older adults, and the immunocompromised are at significantly increased risk for severe disease.

Shigella are less susceptible to destruction by gastric acid than other bacteria when passing through the stomach; a small inoculum, as few as 10 to 100 organisms, may cause disease. After leaving the stomach, Shigella multiply in the small intestine and enter the colon. In the colon, they secrete virulence factors that cause severe inflammation and mediate enterotoxic effects, enabling colonization and invasion of the colonic epithelium. Shigella produces 3 enterotoxins that cause watery or bloody diarrhea and infection-associated symptoms, eg, tenesmus, malaise, and fever.

The average incubation period of Shigella 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. Supportive care may be required, and antibiotics could shorten the duration of illness or prevent complications, particularly in individuals at increased risk for severe disease and complications, eg, hemolytic-uremic syndrome and postreactive arthritis. However, antibiotic resistance is rising within the genus, and extensively drug-resistant Shigella have been identified. Antimicrobial susceptibility testing is critical to ensure appropriate therapeutic selection.