This is a retrospective case:control study examining the use of adjunctive bezlotoxumab to standard C. difficile infection (CDI) treatment compared to standard CDI treatment alone in patients with CDI seen in an academic medical center's specialty outpatient clinic.

This specialty clinic is a unique practice setting where patients with ≥1 recurrent CDI and/or refractory disease are referred. The study will represent real-world data on the clinical use of bezlotoxumab as adjunctive therapy in combination with vancomycin or fidaxomicin for the treatment of patients with recurrent CDI. Retrospective chart review will be conducted for patients who visited the specialty CDI clinic between 1/1/2005 through 12/5/2019. Case patients will be defined as patients who have received bezlotoxumab 10 mg/kg intravenously in addition to standard CDI treatment. Controls will be defined as patients who have received only standard CDI treatment and will be enrolled in a 2:1 ratio to cases. The primary outcome is recurrence of CDI. Recurrence is defined as a new episode of C. difficile infection that occurs after the initial clinical cure of the baseline episode within 12 weeks of receipt of bezlotoxumab or standard CDI treatment. Clinical cure is defined as no diarrhea for 2 consecutive days after completion of standard-of-care CDI therapy. Recurrent CDI will be diagnosed via clinical signs and symptoms and CDI diagnostic assay.

Inclusion Criteria (Cases):

• Age 18 years and older
• Diagnosis of C. difficile infection by clinical signs and symptoms and/or C. difficile diagnostic assay
• Received bezlotoxumab in addition to standard CDI treatment

Inclusion Criteria (Controls):

• Age 18 years and older
• Diagnosis of C. difficile infection by clinical signs and symptoms and/or C. difficile diagnostic assay
• Received only standard CDI treatment

Exclusion Criteria:

• Diarrhea due to causes other than C. difficile
• Incomplete documentation in the electronic medical record

Patients being treated for C. difficile infection