Fig. 2. Flowchart of patient enrollment and disease severity stratification. Patients with confirmed CDI (n = 908) were stratified into non-severe CDI controls (n = 423) and severe CDI cases (n = 485). Severe cases comprised three mutually exclusive subgroups: severe CDI only (n = 156), severe-complicated CDI only (n = 200), and patients meeting both sets of criteria (n = 129). CDI, Clostridioides difficile infection; PCR, polymerase chain reaction.