Microbiology · Year 2 · from Microbiology

Case 3: Clostridioides difficile Infection After Antibiotic Use

Presentation

A 68-year-old woman presents with profuse watery diarrhea (8-10 episodes daily), abdominal cramping, and low-grade fever. She was discharged from the hospital 10 days ago after treatment for community-acquired pneumonia with a 5-day course of levofloxacin. Her current medications include a proton pump inhibitor for GERD. Examination reveals diffuse abdominal tenderness without peritoneal signs. Laboratory studies show WBC 18,000/μL with 15% bands, creatinine 1.6 mg/dL (baseline 0.9), and albumin 2.8 g/dL. Stool testing is positive for C. difficile toxin by PCR and enzyme immunoassay for toxin A/B.

Clinical Image

Colonoscopic image demonstrating pseudomembranous colitis with characteristic yellow-white plaques adherent to the colonic mucosa, pathognomonic for Clostridioides difficile infection.

Image Source: Lecture image - C. difficile pathology

Questions

  1. What is the mechanism by which fluoroquinolones predispose to C. difficile infection?
  1. What factors make this a case of severe or fulminant C. difficile infection?
  1. What is the appropriate antimicrobial treatment for this patient?
  1. What strategies can prevent C. difficile infection in hospitalized patients?

Answers

  1. Mechanism of fluoroquinolone predisposition: Fluoroquinolones and other broad-spectrum antibiotics cause disruption of the normal gut microbiome (dysbiosis), eliminating bacteria that normally:
  • Compete with C. difficile for nutrients and colonization sites
  • Produce short-chain fatty acids that inhibit C. difficile growth
  • Maintain colonization resistance through various mechanisms

Fluoroquinolones are particularly associated with CDI because:

  • They have potent activity against normal gut anaerobes
  • A hypervirulent strain (NAP1/BI/027) emerged with fluoroquinolone resistance, allowing it to proliferate during fluoroquinolone therapy
  • The elderly and hospitalized populations most likely to receive fluoroquinolones are also at highest CDI risk

Additional risk factors in this patient include recent hospitalization, advanced age, and PPI use (which reduces gastric acid barrier to ingested spores).

  1. Severity assessment: This case meets criteria for severe CDI based on:
  • WBC >15,000/μL (she has 18,000)
  • Creatinine >1.5 mg/dL or >1.5x baseline (she has 1.6, which is >1.5x her baseline of 0.9)
  • Hypoalbuminemia (albumin 2.8 g/dL)

Fulminant (previously called severe-complicated) CDI would additionally include hypotension, ileus, megacolon, or need for ICU admission. Prompt recognition of severe CDI is critical because it requires different treatment than non-severe cases.

  1. Appropriate antimicrobial treatment: For severe CDI, current IDSA/SHEA guidelines recommend:
  • Fidaxomicin 200 mg orally twice daily for 10 days (preferred) - narrow spectrum, less microbiome disruption, lower recurrence rate
  • OR Vancomycin 125 mg orally four times daily for 10 days - also highly effective

Key points:

  • Oral vancomycin, NOT IV vancomycin - IV vancomycin does not reach the colon in therapeutic concentrations
  • Metronidazole is NOT recommended for initial treatment of CDI (inferior efficacy, higher failure rates)
  • Discontinue the inciting antibiotic if possible (levofloxacin is already completed)
  • For fulminant CDI, add IV metronidazole to oral vancomycin and consider surgical consultation
  • Bezlotoxumab (anti-toxin B monoclonal antibody) can be considered for high recurrence risk
  1. Prevention strategies:
  • Antimicrobial stewardship: Limit unnecessary antibiotic use, especially fluoroquinolones, clindamycin, and broad-spectrum cephalosporins
  • Hand hygiene: Soap and water (alcohol-based sanitizers do not kill C. difficile spores)
  • Contact precautions: Gown and gloves for contact with CDI patients
  • Environmental cleaning: Sporicidal disinfectants (bleach-based) for rooms of CDI patients
  • Minimize PPI use when not clearly indicated
  • Probiotics: Evidence is mixed; may have modest benefit for primary prevention in high-risk patients
  • Early isolation: Isolate patients with diarrhea pending test results

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