- Clinical science
Escherichia coli (E. coli) is a gram-negative, rod-shaped flagellated bacterium. Although it is an essential component of the bacterial gut flora, disease may be caused by direct intake of a pathogenic E. coli subtype (e.g., in contaminated food) or spreading of the intestinal bacteria to another organ (cystitis, pneumonia). Enterohemorrhagic E. coli (EHEC), for instance, can lead to severe colitis and hemolytic-uremic syndrome (HUS), particularly in children and infants. In such cases, diarrhea should only be treated symptomatically, as antibiotics can lead to increased toxin secretions that exacerbate the course of disease. Supportive therapy without antibiotic therapy is also recommended for infection involving other strains of E. coli (ETEC, EPEC, and EIEC), but antibiotics may be indicated in certain cases.
Pathogen: () bacterium
- Gram-negative, rod-shaped, and flagellated
- Various pathogenic strains of E. coli include:
- Some strains are an essential component of the bacterial gut flora and even have a protective effect against enteropathogens.
- Contaminated food (e.g., raw meat products, vegetables, fruits) and water
- Diagnostic steps: culture and/or PCR from stool samples (if indicated and available)
General guidelines for treating E. coli infections
- Provide supportive therapy
Antibiotic therapy for E. coli: Although some indications exist, antibiotic therapy is generally not recommended and is strongly contraindicated in EHEC!
- Considered only in cases of severe and/or persistent diarrhea (see the individual sections below for specific indications)
- First-line agents in adults: fluoroquinolones (e.g., ciprofloxacin, norfloxacin, levofloxacin, and moxifloxacin)
- Alternative (drug of choice in children and pregnant women): azithromycin
- Differential diagnosis: See , , , and .
- Pathogen: enterohemorrhagic Escherichia coli (EHEC) bacterium
Contaminated food (associated with industrial food production in developed countries)
- Raw beef and milk
- Raw vegetables
- Fecal-oral: through contact with contaminated stool
- At-risk groups: infants/toddlers and the elderly
- Contaminated food (associated with industrial food production in developed countries)
- EHEC bacteria are infected by bacteriophages that integrate their genes into the bacteria's genome; these genes then code for toxins (verotoxin/Shiga toxin 1 and 2).
- Adhesion to receptors of gut cells → Shiga-like toxin secretion → toxin cleaves adenine from the rRNA → inactivation of the 60S subunit → protein synthesis inhibited → cell death → necrosis and inflammation of the GI mucosa → watery-bloody diarrhea with mucus (otherwise known as dysentery)
- See for the role of EHEC in its pathophysiology
- Incubation period: 2–10 days
- Clinical features
- Obligation to report: EHEC infection and HUS infection are reportable in most US states.
- Complications: (particularly in infants/toddlers )
Pathophysiology: ETEC produces heat-labile as well as heat-stable enterotoxins.
- Heat-labile enterotoxin (AB toxin; two-component protein, similar to cholera toxin): activation of adenylate cyclase → ↑ cAMP-level → increased chloride secretion → water efflux into intestinal lumen (secretory diarrhea)
- Heat-stable enterotoxin: activation of guanylate cyclase → ↑ cGMP-level → decreased NaCl reabsorption → water efflux into intestinal lumen (secretory diarrhea)
- Clinical presentation: symptoms last 3–4 days
- Enteropathogenic Escherichia coli (EPEC) leads to infantile diarrhea.
- Adults are less susceptible to EPEC infection.
- Endemic location
- Pathophysiology: EPEC blocks absorption by attaching to the apical surfaces of intestinal epithelium, causing the villi to flatten. No toxin production is involved.
- 10–20 watery bowel movements per day for about two weeks
- Low-grade fever
- Enteroinvasive Escherichia coli (EIEC) causes dysentery.
- Pathophysiology: Invasion of gut epithelium leads to inflammation and necrosis.
- Clinical presentation
- Treatment: See .