Clinical meaning
Clostridioides difficile (formerly Clostridium difficile) is a gram-positive, spore-forming, anaerobic bacterium that is the most common cause of healthcare-associated infectious diarrhea. It is responsible for nearly all cases of pseudomembranous colitis and a significant proportion of antibiotic-associated diarrhea. C. difficile infection (CDI) ranges from mild diarrhea to fulminant colitis with toxic megacolon and death. The pathogenesis requires two key events: disruption of the normal colonic microbiome (usually by antibiotics) and acquisition of toxigenic C. difficile organisms. The normal intestinal flora provides colonisation resistance - a diverse community of bacteria that competitively excludes pathogens. Antibiotics disrupt this protective barrier, creating an ecological niche for C. difficile colonisation. Virtually any antibiotic can cause CDI, but the highest-risk agents are fluoroquinolones (ciprofloxacin, levofloxacin), clindamycin, broad-spectrum cephalosporins, and carbapenems. Even a single dose of a high-risk antibiotic can predispose to CDI. The risk persists for up to 3 months after antibiotic exposure as the microbiome recovers. C. difficile is transmitted via the fecal-oral route, primarily through spores. The vegetative bacteria are killed by oxygen and gastric acid, but the spores are extraordinarily resistant: they...