Background
- Gram-negative bacillus within the family Enterobacteriaceae and order Enterobacterales
- Species include Shigella dysenteriae, Shigella sonnei, Shigella flexneri, and Shigella boydii
- Strains that encode Shiga toxin include Shigella dysenteriae serotype 1 (most common), Shigella flexneri type 2a, Shigella dysenteriae type 4, and Shigella sonnei
- Automated methods frequently misidentify as Escherichia coli, so needs phenotypic testing with serology
- Needs azithromycin susceptibility to be requested specifically, if it is resistant to others
- However, there are no standardized breakpoints, so you have to use the epidemiologic cutoff values
- Extensively drug resistant (XDR) Shigella is resistant to ampicillin, fluoroquinolones, third-generation cephalosporins, azithromycin, and co-trimoxazole
Clinical Manifestations
- Most commonly causes self-limited diarrheal illness with watery or loose stools
- Disease may be more severe, including high fever, abdominal cramps, abdominal tenderness, tenesmus, mucoid stools, and hematochezia
- Complications of severe disease include bacteremia, pseudomembranous colitis, toxic megacolon, intestinal perforation, hemolysis, and hemolytic-uremic syndrome
- Bacteremia more common in neonates and patients with malnutrition
- Serotype 1 is more likely to cause severe illness
Post-Infectious Complications
Diagnosis
- Molecular testing with PCR of stool is the most common method of diagnosing diarrheal illness
- Culture of stool or rectal swab
- Mass spectrometry cannot reliably differentiate from Escherichia coli, so needs biochemical identification
Management
- Supportive care and oral rehydration
- Avoid antidiarrheal or antimotility agents, which can prolong the clinical course and increase risk of severe disease
- If severe disease or immunocompromised, should be treated empirically with antimicrobials
