CDI

Clostridioides difficile infection (CDI) is an infection of the colon caused by the anaerobic bacterium Clostridioides difficile. C. difficile forms spores and produces toxins A and B that disrupt the intestinal lining and trigger inflammation. CDI most commonly occurs after disruption of the normal gut microbiota, typically due to antibiotic exposure, and is a leading cause of antibiotic-associated diarrhea in healthcare settings. Health care facilities and long-term care environments are common settings for transmission.

Clinical presentation ranges from mild diarrhea to severe colitis. Typical symptoms include profuse watery diarrhea, abdominal cramps, and fever; nausea or reduced appetite may occur. In severe cases, pseudomembranous colitis, ileus, or toxic megacolon can develop. In older adults and those with immune suppression or serious comorbidities, CDI can be more severe and associated with higher mortality.

Diagnosis relies on detecting C. difficile toxin or organism in stool, using toxin immunoassays, nucleic acid amplification tests, or a multi-step algorithm. Testing is usually reserved for patients with relevant symptoms who are at risk for CDI. Endoscopy or imaging may be used in complicated cases or when the diagnosis is uncertain.

Treatment depends on severity. First episode without significant comorbidity is treated with oral vancomycin or fidaxomicin; metronidazole is generally not preferred. Severe or fulminant cases require higher-dose oral vancomycin, with adjunctive intravenous metronidazole in some guidelines. Recurrent CDI is common; options include prolonged vancomycin regimens, fidaxomicin, or fecal microbiota transplantation for select patients. Preventive measures include antibiotic stewardship, contact precautions, hand hygiene, and environmental cleaning with sporicidal agents.