Five-Day Treatment with B. licheniformis Along with Classical Vancomycin Treatment Was Effective in Preserving Gut Microbiota in Patients with Clostridioides difficile Infection

Background/Objectives: Clostridioides difficile infection (CDI) is an important nosocomial diarrheal disease. The benefits of the probiotic Bacillus licheniformis (B. licheniformis) in the preservation of intestinal microbiota have not been studied in patients with CDI to date. Therefore, we aimed to investigate the efficacy of B. licheniformis in preserving the intestinal microbiota in patients with CDI. Methods: A multicenter, randomized, placebo-controlled trial was carried out at six academic centers in Korea. Individuals diagnosed with mild to moderate CDI were included in this trial. CDI was treated with vancomycin 125 mg four times daily for two weeks. Along with vancomycin, B. licheniformis was administered for five days in this study, while a placebo was given to the placebo group. Microbiome analysis was performed before and five days after administering vancomycin and B. licheniformis or placebo, using 16S rRNA amplicon sequencing. Alpha and beta diversity was compared between the two groups. Results: A total of 35 participants were finally included in this study, with 16 in the study group and 19 in the placebo group. The alpha diversity was similar in both groups before CDI treatment. After five days of the administration of vancomycin and B. licheniformis or placebo, alpha diversity did not decrease in the study group (Chao1 index, p = 0.665; observed features, p = 0.692). In contrast, alpha diversity decreased in the placebo group (Chao1 index, p = 0.011; observed features, p = 0.011). Beta diversity did not differ between the two groups. Conclusions: The addition of B. licheniformis to vancomycin was effective in preserving gut microbiota in patients with CDI.