Can You Treat C. diff with Oral Vancomycin in a Patient with VRE Bacteremia?
Yes, you can and should treat C. difficile infection with oral vancomycin even in patients with VRE bacteremia, because oral vancomycin is not systemically absorbed and will not affect the VRE bloodstream infection, while it remains the most effective treatment for severe CDI. 1, 2
Key Pharmacologic Principle
- Oral vancomycin is minimally absorbed from the gastrointestinal tract, achieving high concentrations in the colon but negligible systemic levels, meaning it will not provide any therapeutic benefit for VRE bacteremia but also will not worsen systemic VRE resistance patterns. 1
- Intravenous vancomycin provides no therapeutic benefit for CDI because it is not excreted into the colon in sufficient concentrations to treat the infection. 2, 3
Treatment Algorithm for CDI with Concurrent VRE Bacteremia
Step 1: Assess CDI Severity
- Severe CDI is defined by: temperature >38.5°C, WBC >15,000 cells/μL, serum creatinine >1.5 mg/dL, albumin <2.5 g/dL, or ≥10 bowel movements in 24 hours. 1, 2
- Fulminant CDI includes hypotension, shock, end-organ failure, ileus, toxic megacolon, or colonic perforation. 1, 2
Step 2: Select CDI Treatment Based on Severity
- For severe or fulminant CDI: Use oral vancomycin 125 mg four times daily for 10 days (or 500 mg four times daily for fulminant cases). 1, 3
- For non-severe CDI: Fidaxomicin 200 mg twice daily for 10 days is preferred over vancomycin when available, as it has lower VRE acquisition rates (7% vs 31%). 1, 2
- Metronidazole should only be used when both vancomycin and fidaxomicin are unavailable, and only for non-severe CDI, as it has significantly lower cure rates for severe disease (OR 0.46,95% CI 0.26-0.80). 4, 2
Step 3: Treat VRE Bacteremia Separately
- The VRE bacteremia requires systemic antibiotics (such as linezolid or daptomycin) that are entirely separate from the oral vancomycin used for CDI. 1
- Oral vancomycin will not treat the VRE bacteremia because it is not absorbed systemically. 1, 2
Addressing the VRE Concern
Evidence on Oral Vancomycin and VRE Risk
- A large retrospective cohort study of 10,137 patients found that oral vancomycin was no more likely to cause VRE infection within 3 months compared to metronidazole (adjusted RR 0.96,95% CI 0.77-1.20), with an absolute risk difference of only -0.11%. 5
- Both oral metronidazole and oral vancomycin promote VRE overgrowth during CDI treatment, with no significant difference between the two agents (14% vs 8% new VRE detection, p=1.0). 6
- Fidaxomicin has the lowest impact on VRE, with significantly lower VRE acquisition rates (7%) compared to vancomycin (31%, p<0.001), making it the preferred choice when VRE is a major concern. 1
Clinical Reality
- The patient already has VRE bacteremia, so the concern about promoting VRE colonization is less relevant than ensuring effective CDI treatment to prevent mortality. 1
- Severe CDI has a significantly lower 30-day mortality when treated with vancomycin compared to metronidazole, making vancomycin the priority for severe disease regardless of VRE status. 1
Common Pitfalls to Avoid
- Do not withhold oral vancomycin due to VRE concerns when treating severe or fulminant CDI, as the mortality benefit of effective CDI treatment outweighs theoretical VRE risks. 1, 2
- Do not use IV vancomycin alone for CDI, even in patients who cannot take oral medications; instead, use oral or rectal vancomycin plus IV metronidazole if needed. 1, 2
- Do not assume oral vancomycin will worsen VRE bacteremia, as it is not systemically absorbed and will not affect bloodstream VRE. 1, 5
- Consider fidaxomicin as the preferred alternative if the CDI is non-severe and you want to minimize VRE selection pressure, but do not compromise CDI treatment efficacy. 1, 2