As a primary care physician, how should I manage a 59-year-old patient with persistent diarrhea after short courses of amoxicillin‑clavulanate (Augmentin) and azithromycin (Z‑Pack), pending repeat Clostridioides difficile testing?

Management of Persistent Diarrhea After Brief Antibiotic Courses with Negative C. difficile Testing

Stop all antibiotics immediately and focus on symptomatic management with probiotics and dietary modifications while awaiting repeat C. difficile testing, as antibiotic-associated diarrhea without confirmed CDI does not require specific antimicrobial treatment.

Immediate Actions

Your patient's diarrhea is most likely antibiotic-associated diarrhea (AAD) without C. difficile infection, given the negative initial test. Both amoxicillin-clavulanate and azithromycin are well-known causes of AAD 1, 2. The FDA label for Augmentin explicitly warns that "diarrhea is a common problem caused by antibiotics which usually ends when the antibiotic is discontinued" 1.

Key Steps:

1. Discontinue all antibiotics - This is the single most important intervention for AAD 3, 2

2. Proceed with repeat C. difficile testing - While guidelines advise against routine repeat testing within 7 days 4, 5, your clinical scenario justifies it given:

   • Persistent symptoms after antibiotic discontinuation
   • Sequential antibiotic exposures (both Augmentin and azithromycin are CDI risk factors) 6
   • The initial test may have been a false negative (EIA sensitivity ranges 50-90%) 7

3. Do NOT empirically treat for C. difficile - With a negative test and no severe disease markers (no fever, no leukocytosis >15,000, no elevated creatinine), empirical CDI treatment is not indicated 4, 8

Symptomatic Management for Diarrhea

For immediate symptom relief while awaiting test results:

• Probiotics: Consider Saccharomyces boulardii or Enterococcus SF68, which have evidence for reducing antibiotic-associated diarrhea 2
• Dietary modifications: Avoid foods high in poorly absorbable carbohydrates (lactose, sorbitol, fructose) 2
• Psyllium fiber: Can be used to bulk stools once acute diarrhea improves 8
• Avoid antidiarrheals initially: Do not use loperamide or other antimotility agents until C. difficile is definitively ruled out

Do NOT use cholestyramine or bile acid binders - these should not be used as monotherapy and can interfere with vancomycin if CDI treatment becomes necessary 8.

If Repeat C. difficile Test is Positive

Should the repeat test return positive, this would represent a first episode of CDI (not recurrence, as the initial test was negative):

• First-line treatment: Fidaxomicin 200 mg twice daily for 10 days 9, 8
• Alternative: Vancomycin 125 mg four times daily for 10 days 4, 9
• Avoid metronidazole for initial episodes unless resource constraints exist 9, 8

If Repeat C. difficile Test Remains Negative

This confirms non-C. difficile antibiotic-associated diarrhea:

• Reassure the patient that symptoms typically resolve within days to 2 weeks after antibiotic cessation 1, 2
• Continue probiotics for 2-4 weeks
• Monitor for resolution - most mild AAD resolves with antibiotic discontinuation alone 2
• Consider alternative diagnoses if diarrhea persists beyond 2-3 weeks (inflammatory bowel disease, microscopic colitis, celiac disease)

Critical Red Flags Requiring Immediate Action

Contact the patient immediately if she develops:

• Bloody or severe watery diarrhea (>10 stools/day)
• Fever >101°F
• Severe abdominal pain or distension
• Signs of dehydration (dizziness, decreased urine output)

These would indicate potential severe CDI or other serious complications requiring urgent evaluation 1.

Prevention of Future Episodes

Counsel the patient on:

• Antibiotic stewardship: Future antibiotics should be used only when absolutely necessary 4, 8
• Handwashing: Soap and water (not alcohol-based sanitizers) if CDI is confirmed 4
• Proton pump inhibitor review: If she's on PPIs, evaluate necessity but don't discontinue if legitimately indicated 4, 8

Common Pitfall to Avoid

Do not order multiple sequential C. difficile tests beyond this single repeat test. If the second test is negative and symptoms persist, the diagnosis is not CDI 4, 5, 7. Repeated testing increases false positives from detecting asymptomatic colonization rather than active infection.

The patient's brief antibiotic courses (2-3 days each) actually reduce her CDI risk compared to longer exposures, but both agents she received are known CDI triggers 6. The key is that 80-90% of antibiotic-associated diarrhea is NOT due to C. difficile 2, and most cases resolve spontaneously with supportive care after stopping the offending antibiotic.