Shigella infection (shigellosis)
Shigella infection is a highly contagious bacillary dysentery caused by a very low inoculum of an invasive gram-negative rod, presenting with fever, crampy abdominal pain, tenesmus, and small-volume bloody or mucoid diarrhea. Diagnosis rests on stool culture or molecular testing, and unlike most enteric infections, antibiotics are indicated to shorten illness and limit person-to-person spread.
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What this article covers
- Overview
Definition: shigellosis is an acute bacillary dysentery caused by Shigella species, gram-negative rods that invade the colonic mucosa and produce fever, crampy abdominal pain, tenesmus, and small-volume bloody and/or mucoid diarrhea.
- Epidemiology
Person-to-person transmission dominates: spread most commonly occurs directly between people through the fecal-oral route because of the very low infectious dose, and also through contaminated food or water.
- Risk factors
Close person-to-person contact: households, daycare, and institutional settings where the low infectious dose allows efficient spread.
- Pathophysiology
Ingestion of a very small inoculum: fewer than 100 organisms survive gastric acid and reach the colon, which is why direct person-to-person transmission is so efficient.
- Clinical features
Dysentery syndrome: crampy abdominal pain, tenesmus, and small-volume bloody and/or mucoid diarrhea, the hallmark presentation.
- Differential diagnosis
Nontyphoidal Salmonella infection: watery or inflammatory diarrhea with fever, but generally self-limited and typically not treated with antibiotics, unlike shigellosis (Salmonella).
- Diagnosis
Confirm with stool culture or stool molecular testing (NAAT/PCR): identification of Shigella on routine stool culture or nucleic acid amplification/PCR panel establishes the diagnosis; culture…
- Management
Start oral rehydration first in every patient: replace fluid and electrolyte losses; most cases of shigellosis are self-limited and rehydration is the universal first step regardless of antibiotic decision.
- Complications
Hemolytic uremic syndrome: driven by Shiga toxin, most classically from S.
- Prognosis
Generally favorable: most cases of shigellosis are self-limited and resolve, particularly with prompt antibiotic treatment in those who need it.
- Prevention
Hand hygiene: rigorous handwashing with soap and water after toilet use, diaper changes, and before food preparation, given the very low infectious dose required for transmission.
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