Shigella/Enteroinvasive E. coli - Information for Clinicians
Type of infection
Shigella is a facultative gram-negative bacillus. Includes Shigella sonnei (most common), S. flexneri, S. boydii, S. dysenteriae (most virulent). S. dysenteriae type 1 also produces shiga toxin and causes severe disease. Enteroinvasive E. coli (EIEC) are virtually identical to Shigella and cannot be differentiated by molecular assays and so are reported together. In the US most detections will likely be Shigella spp., but EIEC may be seen in travelers.
Sources of infection
- Humans are the natural host and reservoir of Shigella.
- Most transmission is fecal oral. Shigella has a very low infectious dose (~10 organisms).
- Sexual transmission can occur.
- Risk factors include attendance at day care, travel, and contact with children <5 years of age.
- Day care outbreaks are common; foodborne outbreaks and recreational water outbreaks occur but are more unusual.
Usual symptoms
- Incubation period is 24-72 hours.
- Diarrhea, sometimes with blood or mucous, stomach pain or cramps, tenesmus, and fever. Diarrhea can be watery, especially with S. sonnei.
Duration of illness
- Typically 2-7 days without treatment.
Treatment
- Prevent dehydration.
- Avoid antimotility agents (loperamide [Immodium] or diphenoxylate with atropine [Lomotil]) in children with Shigella.
- Antibiotics may shorten the duration of illness and shedding. Treatment is recommended for patients with severe disease, dysentery, or underlying immunosuppressive conditions.
- Increasing antimicrobial resistance makes empiric antibiotic selection difficult. Up to 40% are resistant to ampicillin and trimethoprim sulfamethoxazole. Azithromycin, flouroquinolones (5 day course) or ceftriaxone (2 day course) are likely to be adequate.
Complications
- Reactive arthritis and Reiter's syndrome.
- Bacteremia is rare but can occur in infants, the severely malnourished, and in patients with S. dysenteriae type 1.
- Toxic megacolon, intestinal perforation.
- Seizures have been reported, usually in young children with high fever.
- Hemolytic uremic syndrome (HUS) is a rare complication usually associated with S. dysenteriae type 1.
Comments
- People with Shigella shed for up to 2 weeks after illness onset.
- Secondary spread is common. Instruct patients and families in good hand hygiene using the bathroom, changing diapers, and before and after cooking.
- Patients should avoid swimming pools or water parks until they have fully recovered.
- People with diarrhea should not prepare food.
- Report cases to the local health department.
- Children with Shigella should not return to day care until cleared by the local health department.