C. difficile causes severe watery diarrhea and inflammation of the colon, and it can be dangerous when missed. According to the CDC, C. difficile causes 15 to 25 percent of all antibiotic-associated diarrhea. The agency identifies fluoroquinolones, third- and fourth-generation cephalosporins, clindamycin and carbapenems as carrying particular risk, along with prior C. difficile infection and age 65 or older. C. difficile infections in U.S. emergency departments fell 30 percent overall from 2014 to 2024, but rose 59 percent among adults aged 18 to 24, based on about 38 million visits and nearly 150,000 cases. What causes C. difficile infection?