C. difficile Infection in Hospitalized Patients: Who to Test, How to Grade It, and How to Treat It

Bottom line

Who to test and who not to test

• Test symptomatic patients only: 3 or more unformed stools in 24 hours with no alternative explanation. Do not test formed stool, asymptomatic patients, or anyone who received laxatives within 48 hours — colonization is common and a positive result in those settings leads to unnecessary treatment.
• Do not repeat testing within 7 days and never send a test of cure; toxin and PCR positivity persist after clinical cure. Repeat stool testing is reasonable only if symptoms persist or worsen after therapy.
• Exclude mimics before attributing diarrhea to C. difficile: tube feeds, laxatives and osmotic agents, and other enteric pathogens when epidemiology suggests them.

Severity classification

• Non-severe: diarrhea without the markers below.
• Severe: white cell count 15,000 or higher, or creatinine above 1.5 mg/dL (IDSA/SHEA) or above 1.5 times baseline (AGA) — the two societies differ slightly, and either threshold marks higher recurrence risk and worse outcomes.
• Fulminant: hypotension or shock, ileus, or toxic megacolon. These patients need urgent escalation of care and surgical consultation.
• Labs at diagnosis and serially: CBC with differential, BMP (white count, creatinine), lactate, and albumin. Image with CT (or at least a plain film) only for distension, severe pain, ileus, a rising white count, or deterioration, looking for colonic wall thickening, a colon over 6 cm, or perforation.

Acute management of a first episode

• Fidaxomicin 200 mg orally twice daily for 10 days is preferred (equivalent cure, lower recurrence); vancomycin 125 mg orally four times daily for 10 days is an acceptable alternative when fidaxomicin is unavailable or cost-prohibitive. Complete the full course even if stools normalize early.
• Metronidazole is not used as monotherapy outside fulminant disease or when oral agents cannot be given. IV vancomycin does not reach the colon and does not treat C. difficile; oral vancomycin is minimally absorbed and needs no levels or renal adjustment.
• Stop the inciting antibiotic when the original infection has been adequately treated. If ongoing therapy is required, narrow to the lowest-risk, susceptibility-guided agent for the shortest course. The highest-risk classes are clindamycin, fluoroquinolones, third- and fourth-generation cephalosporins, and carbapenems.
• Discontinue proton pump inhibitors without a clear indication, and stop antimotility agents (loperamide, diphenoxylate) and unnecessary laxatives or stool softeners.
• Supportive care: isotonic fluids for volume loss and any creatinine rise, repletion of potassium and magnesium, holding or reducing nephrotoxins and diuretics, and stool charting every shift.

Fulminant disease

• Vancomycin 500 mg orally or by nasogastric tube four times daily plus metronidazole 500 mg IV every 8 hours; add vancomycin 500 mg in 100 mL of saline as a retention enema every 6 hours when ileus is present.
• Urgent surgical consultation and ICU-level care. Subtotal colectomy with end ileostomy, or a diverting loop ileostomy with colonic lavage, is indicated for perforation, megacolon, worsening organ failure, or failure to improve.
• If there is no clinical improvement after about 5 days of appropriate therapy in non-fulminant disease: image for ileus or megacolon, confirm the oral drug is actually being delivered (not held for NPO status), reconsider alternative diagnoses, consult infectious diseases, and consider switching vancomycin to fidaxomicin or escalating to high-dose vancomycin with IV metronidazole.

Recurrence

• A first recurrence within 8 weeks: fidaxomicin (a standard 10-day course or an extended pulse regimen) if vancomycin was used initially, or a tapered and pulsed oral vancomycin regimen — 125 mg four times daily for 10–14 days, then twice daily for a week, daily for a week, then every 2–3 days for 2–8 weeks.
• Bezlotoxumab 10 mg/kg IV once can be added to standard-of-care antibiotics for patients at high recurrence risk (age 65 or older, immunocompromise, a severe episode, prior recurrence); use caution in heart failure. It is an adjunct, never monotherapy.
• A second or later recurrence (third episode onward): a standard antibiotic course followed by fecal microbiota-based therapy, either conventional transplant or an FDA-approved live biotherapeutic.
• Before discharge: avoid future unnecessary antibiotics and proton pump inhibitors, discuss oral vancomycin prophylaxis with infectious diseases if systemic antibiotics will be needed again, document the episode prominently, and counsel the patient and family on hand washing and prompt reporting of recurrent diarrhea.

Infection control

• A private room with contact precautions for the duration of diarrhea and at least 48 hours after it resolves; gowns and gloves for every entry.
• Soap-and-water hand washing — alcohol-based sanitizer does not kill spores.
• Dedicated equipment and sporicidal (bleach) room disinfection; notify infection control.

Monitoring and disposition

• Daily stool frequency and consistency chart, vital signs, and abdominal exam; CBC and BMP daily until the white count and creatinine trend down, then every 48 hours. Expect improvement in stool frequency and fever within 3–5 days.
• Manage on a medical ward under contact precautions; step-down or ICU for hemodynamic instability, ileus, or megacolon.
• Discharge when stools are decreasing, the patient is afebrile with improving white count and creatinine and tolerating oral intake, and the remaining days of the course are arranged as an outpatient. Follow-up with primary care or infectious diseases within 1–2 weeks, with instructions to call immediately if watery diarrhea returns within 8 weeks.

Escalate care if

• Hypotension or shock, ileus, or toxic megacolon develops — fulminant disease: high-dose oral vancomycin plus IV metronidazole, rectal vancomycin for ileus, surgical consultation, and ICU-level care.
• The white count rises further, lactate climbs, creatinine doubles, or abdominal distension or peritoneal signs emerge — treat as fulminant and obtain surgery and infectious diseases consults immediately.
• No improvement after 5 days of appropriate therapy — image, confirm drug delivery, reconsider the diagnosis, and consult infectious diseases.
• Diarrhea persists after a full course while the colitis is clearly resolving — consider post-infectious diarrhea, tube-feed intolerance, or another cause rather than re-treating or retesting.

Duration

Ten days for an initial episode, extended to 14 days or longer with a slow response or when concomitant systemic antibiotics must continue. A tapered and pulsed vancomycin regimen for a first recurrence runs 6–8 weeks.

Caveats

• Metronidazole monotherapy is inappropriate for severe disease; it is reserved for fulminant disease (IV, as an adjunct) or when oral agents cannot be given.
• Avoid antimotility agents in active colitis because of megacolon risk.
• Alcohol-based hand sanitizer does not kill C. difficile spores — soap and water is required.
• Bezlotoxumab is used with caution in heart failure because of increased heart-failure events.
• This pathway assumes the diarrhea is not attributable to laxatives, tube feeds, or another cause and that no ileus is present at diagnosis.

References

1. Management of Clostridioides difficile infection in adults. (2026) · Primary guideline“White blood cell count >15,000 cells/uL and/or creatinine >1.5 × baseline are indicative of severe CDI and increased risk for recurrence and poor outcomes.”
2. AGA Clinical Practice Update on Management of Clostridioides difficile Infection in Adults: Expert Review. (2026) · Guideline-derived“White blood cell count >15,000 cells/uL and/or creatinine >1.5 × baseline are indicative of severe C difficile infection and increased risk for recurrence and poor outcomes.”
3. Biomarkers for Early Severity Prediction in Clostridioides difficile Infection: Current Evidence, Clinical Utility, and Future Directions. (2026) · Narrative review“In IDSA/SHEA criteria, severe CDI is generally supported by a white blood cell count ≥ 15,000 cells/mm³ or serum creatinine > 1.5 mg/dL, while fulminant CDI is characterized by hypotension, shock, ileus, or toxic megacolon and requires urgent escalation of care.”