Enterococci enhance Clostridioides difficile pathogenesis

Area of Science:

• Microbiology
• Gut Microbiome Research
• Infectious Diseases

Background:

• The gastrointestinal tract harbors a complex polymicrobial community influencing host health and disease.
• Microbial interactions are crucial in infections, yet mechanisms by which commensal or pathogenic microbiota affect pathogen virulence are not fully understood.
• Clostridioides difficile infection (CDI) is a major healthcare concern, often exacerbated by disruptions in the gut microbiota.

Purpose of the Study:

• To investigate how the expansion of enterococci, a group of antibiotic-resistant opportunistic pathogens, impacts the fitness and pathogenesis of Clostridioides difficile.
• To elucidate the metabolic mechanisms underlying the interaction between enterococci and C. difficile in the gut environment.
• To provide mechanistic insights into the role of pathogenic microbiota in CDI severity.

Main Methods:

• Utilized mouse models of infection to study microbial interactions in vivo.
• Analyzed metabolic changes in the gut environment shaped by enterococci.
• Investigated the reprogramming of C. difficile metabolism in response to enterococcal-derived nutrients and metabolic cues.
• Examined patient samples from individuals with C. difficile infection.

Main Results:

• Expansion of enterococci enhances the fitness and pathogenesis of Clostridioides difficile in the gut.
• Enterococci reshape the gut metabolic landscape through nutrient restriction and cross-feeding, providing fermentable amino acids (leucine, ornithine) that benefit C. difficile.
• Enterococcal depletion of arginine acts as a metabolic cue, increasing C. difficile virulence.
• Microbial interactions between enterococci and C. difficile were observed in mouse models and human CDI patients.

Conclusions:

• Enterococci promote C. difficile pathogenesis by modulating the gut metabolic environment.
• Specific metabolic exchanges, including nutrient provision and depletion, mediate the enhanced virulence of C. difficile in the presence of enterococci.
• These findings highlight the significant role of pathogenic microbiota in driving the severity of C. difficile infections.