Quantitative characterization of Clostridioides difficile population in the gut microbiome of patients with C. difficile infection and their association with clinical factors.

Objective was to analyse bacterial composition and abundance of Clostridioides difficile in gut microbiome of patients with C. difficile infection (CDI) in association with clinical characteristics. Whole metagenome sequencing of gut microbiome of 26 CDI patients was performed, and the relative abundance of C. difficile and its toxin genes was measured. Clinical characteristics of the patients were obtained through medical records. A strong correlation between the abundance of C. difficile and tcdB genes in CDI patients was found. The relative abundance of C. difficile in the gut microbiome ranged from undetectable to 2.8% (median 0.089). Patients with fever exhibited low abundance of C. difficile in their gut, and patients with fewer C. difficile organisms required long-term anti-CDI treatment. Abundance of Bifidobacterium and Bacteroides negatively correlated with that of C. difficile at the genus level. CDI patients were clustered using the bacterial composition of the gut: one with high population of Enterococcus (cluster 1, n = 12) and another of Bacteroides or Lactobacillus (cluster 2, n = 14). Cluster1 showed significantly lower bacterial diversity and clinical cure at the end of treatment. Additionally, patients with CDI exhibited increased ARGs; notably, blaTEM, blaSHV and blaCTX-M were enriched. C. difficile existed in variable proportion of the gut microbiome in CDI patients. CDI patients with Enterococcus-rich microbiome in the gut had lower bacterial diversity and poorer clinical cure.