Clostridioides

Clostridioides is a genus of Gram-positive, obligate anaerobic, spore-forming bacteria in the phylum Firmicutes. The genus was proposed to reclassify species formerly placed in Clostridium, most notably Clostridioides difficile, following phylogenetic analyses that revealed distinct lineages within the traditional genus.

The genus comprises several species that inhabit soil, the gastrointestinal tracts of animals, and occasionally cause disease in humans. The most clinically significant member is Clostridioides difficile, a major cause of antibiotic-associated diarrhea and pseudomembranous colitis. Other species include Clostridioides innocuum and Clostridioides sordellii, which can cause opportunistic infections, particularly in hospital or veterinary settings.

Clostridioides species are Gram-positive, obligate anaerobes that form endospores. They are rod-shaped and may be slow-growing under aerobic conditions; their spores enable persistence in the environment and on surfaces.

In C. difficile, disease is primarily driven by toxins that disrupt intestinal epithelium, notably toxins A and B; some strains produce a binary toxin CDT. Illness typically follows disruption of normal gut microbiota by antibiotics or other factors, enabling colonization and toxin-mediated inflammation.

Spores facilitate survival outside hosts and transmission via contaminated hands, surfaces, and equipment, particularly in healthcare settings.

Infections range from mild diarrhea to life-threatening colitis. Diagnosis combines clinical symptoms with laboratory detection of toxins or bacterial DNA. Treatment depends on severity and may involve targeted antibiotics, discontinuation of inciting agents, and, for recurrent cases, fecal microbiota transplantation.