Dynamics of the microbiota in patients with Clostridioides difficile: Recurrence, treatment, sex, and immunosuppression

BACKGROUND: Alterations in the gut microbiome are central to the pathogenesis and recurrence of Clostridioides difficile infection (CDI). OBJECTIVE: To evaluate intestinal microbiome changes during CDI and their association with recurrence, sex, age, and immunosuppression. METHODS: Patients from the CDI-ANCRAID-SEICV cohort were consecutively enrolled. Stool samples were obtained at diagnosis (Dx), end of treatment (ET), and eight weeks post-treatment (8W) or upon recurrence. Microbiota composition was analyzed by 16S rRNA sequencing using QIIME2 and R. Outcomes were compared by demographics, immunosuppression, and treatment (vancomycin [VNC], vancomycin-bezlotuzumab [VNC-BZL], fidaxomicin [FDX]). RESULTS: Among 143 patients, non-recurrent cases showed higher biodiversity at 8W versus diagnosis (H p = 0.002, ASVs p < 0.001), unlike recurrent cases. Diversity decreased with VNC (H p > 0.001, ASVs p < 0.001) but was preserved with FDX (H p = 0.15). Recovery of Shannon diversity was limited in women (p = 0.50) and immunocompromised patients (p = 0.31). At ET, Fusobacteria and Verrucomicrobiota were less abundant in recurrent than non-recurrent cases (0.77%, 0.53% vs 3.43%, 3.50%). FDX-treated samples showed higher Bacteroidetes (31.33%) compared to VNC (5.23%) or VNC-BZL (3.12%). Women exhibited increased Firmicutes abundance (p = 0.034). CONCLUSIONS: Restoration of microbial diversity correlates with CDI resolution. FDX preserves gut microbiota better than VNC or VNC-BZL. Women and immunocompromised patients demonstrate impaired microbiota recovery.