Escherichia coli (E. coli) infection

Disease Description (Causes and Symptoms)

• Definition: Escherichia coli (E. coli) is a member of the normal intestinal flora, but some pathogenic strains enter the human body through food, water, or contact and cause various clinical manifestations, including enteritis, urinary tract infections, sepsis, and neonatal meningitis. In hot and humid environments, consuming contaminated food or water and unhygienic lifestyle habits (e.g., inadequate handwashing and poor hygiene after defecation), as well as certain sexual contacts, may increase the risk of transmission.
• Main causes: Attachment of pathogenic E. coli strains (ETEC, EPEC, EHEC/STEC, EIEC, UPEC, etc.) to the intestinal mucosa, toxin production, or invasive activity.
• Pathophysiology summary: Depending on the strain, the bacteria attach to the intestinal mucosa and secrete toxins (e.g., heat-stable and heat-labile toxins, Shiga toxin), or cause inflammation and diarrhea through tissue invasion. In urinary tract infections, the bacteria attach to and multiply in the urinary tract, causing inflammation and urinary symptoms; in some cases, they penetrate the bloodstream and cause systemic infection.
• Representative symptoms: Diarrhea (watery or bloody), abdominal pain (cramping), vomiting, nausea, fever, headache, and general malaise. In urinary tract infections: urinary frequency, dysuria, hematuria, and pyuria.

Treatment Methods

• General principles: Most intestinal E. coli infections improve with fluid and electrolyte replacement and symptomatic treatment. If signs of dehydration (dizziness, decreased urine output, rapid pulse, etc.) are present, hospitalization and intravenous fluids may be necessary.
• Drug treatment:
  • Fluid and electrolyte replacement (oral ORS or IV fluids).
  • Antibiotics: Determined according to the strain and clinical presentation.
    • For noninvasive travelers' diarrhea or severe bacterial diarrhea, empiric or test-based antibiotics are selected (e.g., a single dose of a fluoroquinolone or azithromycin in adults) — local resistance patterns and clinical guidelines must be followed.
    • For urinary tract infections (UPEC), antibiotics (e.g., nitrofurantoin, trimethoprim-sulfamethoxazole, fosfomycin, etc.) are selected according to urine culture and susceptibility results.
    • For neonates, sepsis, or severe invasive infections, intravenous antibiotic treatment is provided after hospitalization.
  • Caution: When Shiga toxin-producing E. coli (EHEC/STEC) infection is suspected, antibiotic use may increase the risk of HUS (hemolytic uremic syndrome), so whether to use antibiotics must be assessed carefully. In addition, antidiarrheal drugs (e.g., loperamide) may be contraindicated when toxin-mediated or invasive diarrhea is suspected (possible delayed elimination of pathogens and increased risk of complications).
• Procedures/Surgery: Generally not necessary. However, surgical treatment may be required if complications such as peritonitis or intestinal perforation occur.
• Lifestyle management and precautions:
  • Drink sufficient fluids and get adequate rest.
  • Seek medical attention immediately if a high fever, bloody diarrhea, severe abdominal pain, persistent vomiting, symptoms of dehydration, or neurological symptoms (such as confusion) occur.
  • Practice hand hygiene and food hygiene, and avoid consuming contaminated water.
  • For mothers or neonates, hygienic care (handwashing and cleanliness during feeding) is recommended; because neonates are a high-risk group, consult a doctor to determine isolation and management.

Outpatient Visit Checklist (Including Preparation Items and Example Questions)

• Items to prepare:
  • List of currently used medications (including antibiotics, anticoagulants, immunosuppressants, etc.)
  • Records of recent body temperature, urine output, number of vomiting/diarrhea episodes, and stool characteristics (including watery, bloody, or mucous stools)
  • Recent meal and food intake history (eating out, raw foods, seafood, etc.), recent travel history (domestic or international), and contact with hospitals or long-term care facilities
  • Underlying conditions (diabetes, kidney disease, immunocompromised status, pregnancy, etc.) and previous test results (urine, stool, or blood tests)
  • For children and neonates, breastfeeding status and feeding and bowel movement patterns
• Specimens that may be shown to the doctor during an outpatient visit:
  • Stool sample, if possible (store and submit according to testing instructions)
  • Urine sample (if urinary symptoms are present)
• Example checklist questions (to confirm for yourself before making a medical appointment):
  • Whether symptoms of dehydration (dry lips, decreased urine output, lethargy, etc.) are present
  • Whether there is bloody stool or persistent high fever
  • When the symptoms began and how they have progressed (over several hours/days)
  • Whether antibiotics have recently been used

General Example Questions to Ask the Doctor

• What are the expected effects and common side effects of this medication (the prescribed antibiotic)?
• What additional tests should I undergo for my symptoms (stool culture, Shiga toxin test, urine culture, etc.)?
• When should I go to the hospital (emergency department/hospital admission)? What are the criteria for managing this at home?

Examples of Disease-Specific Questions

• When diarrhea contains blood and is accompanied by a high fever, should antibiotics be started immediately, or should testing be done first?
• If a neonate or mother has diarrhea, is it okay to continue breastfeeding? Should the neonate be isolated?

Additional Information (Summary)

• Department: Infectious Diseases (or Gastroenterology, Pediatrics, or Urology may be involved depending on the clinical situation)
• Complications include hemolytic uremic syndrome (HUS), sepsis, urinary tract complications (pyelonephritis and renal failure), and reactive arthritis; high-risk groups (infants and young children, older adults, and immunocompromised individuals) may experience a more severe course.