What is diarrhea secondary to enteropathic Escherichia coli (E. coli)?

Diarrhea Secondary to Enteropathic E. coli: Definition and Clinical Implications

Diarrhea secondary to enteropathic Escherichia coli (E. coli) refers to intestinal infection with specific pathogenic strains of E. coli that cause diarrheal illness through distinct mechanisms of mucosal damage, toxin production, and inflammatory responses. These infections can range from mild self-limiting diarrhea to severe, potentially life-threatening disease depending on the specific pathotype involved and host factors 1.

Types of Enteropathic E. coli

Enteropathic E. coli can be classified into several distinct pathotypes, each with unique virulence mechanisms:

1. Enteropathogenic E. coli (EPEC):

   • Causes non-inflammatory watery diarrhea
   • Attaches firmly to intestinal mucosa causing "attaching-effacement" lesions
   • Dissolves brush border microvilli in jejunum and ileum
   • Results in loss of brush border disaccharidase enzymes and absorptive surface
   • Major cause of infant diarrhea and neonatal diarrhea 1, 2

2. Enterotoxigenic E. coli (ETEC):

   • Major cause of traveler's diarrhea and infant diarrhea in developing countries
   • Attaches to small intestinal mucosa
   • Produces heat-labile and/or heat-stable toxins
   • Causes watery, non-inflammatory diarrhea 1, 3

3. Enteroinvasive E. coli (EIEC):

   • Causes inflammatory diarrhea and dysentery
   • Invades colonic enterocytes through endocytosis
   • Replicates within cells causing necrosis and mucosal stripping
   • Similar to but usually less severe than Shigella dysentery 1

4. Enterohemorrhagic E. coli (EHEC):

   • Causes hemorrhagic colitis
   • Produces Shiga toxins (verocytotoxins)
   • Can lead to hemolytic uremic syndrome
   • Attaches to terminal ileal and colonic mucosa 1, 3

5. Enteroaggregative E. coli (EAggEC):

   • Causes persistent and chronic diarrhea
   • Damages colonic villi through hemorrhagic necrosis
   • Major cause of chronic diarrhea in children 1

Clinical Presentation

The clinical presentation varies by pathotype but may include:

• Watery diarrhea (EPEC, ETEC)
• Bloody diarrhea (EHEC, EIEC)
• Fever (variable, more common with inflammatory types)
• Abdominal pain and cramping
• Persistent diarrhea lasting >14 days (especially with EAggEC)
• Potential for severe complications like hemolytic uremic syndrome (EHEC) 4

Diagnosis

Diagnosis of enteropathic E. coli infection requires:

• Clinical suspicion based on symptoms and epidemiology
• Stool culture with specific testing for pathogenic E. coli
• Molecular techniques (nucleic acid amplification tests) to identify specific virulence genes
• Toxin detection assays for certain pathotypes 4

The Journal of Travel Medicine notes that standard stool cultures may not detect all enteropathic E. coli types, and specialized testing is often required 4.

Treatment Considerations

Treatment depends on the severity of illness and specific pathotype:

• Rehydration (oral whenever possible) is the cornerstone of management
• Antimicrobial therapy may be indicated for certain types, particularly ETEC (traveler's diarrhea)
• Fluoroquinolones like ciprofloxacin have been traditionally used but increasing resistance is concerning
• Ciprofloxacin is FDA-approved for infectious diarrhea caused by enterotoxigenic E. coli strains 5
• Avoid antimotility agents in cases of bloody diarrhea or suspected EHEC infection 4

Important Caveats

1. Antimicrobial Resistance: Increasing antibiotic resistance among enteropathic E. coli strains is a growing concern, particularly to fluoroquinolones 4.

2. Risk of Complications: Antibiotics may potentially worsen outcomes in certain infections, particularly EHEC, by increasing toxin release 4.

3. Diagnostic Challenges: Specific diagnosis is expensive and time-consuming, often requiring specialized laboratory techniques beyond routine stool culture 1.

4. Chronic Sequelae: Some enteropathic E. coli infections may lead to post-infectious complications including irritable bowel syndrome 4.

The understanding of enteropathic E. coli has evolved significantly over time, with recognition that these pathogens use distinct mechanisms to cause diarrheal disease through specific virulence factors, often encoded on plasmids, that enable intestinal colonization, mucosal damage, and/or toxin production 6, 7.