Clostridium difficile is an organism present as normal flora of the gut. Inflammation of the large intestine can occur after antibiotic use secondary to abnormal growth of clostridium difficile. C. difficile releases toxins that causes inflammation and bleeding in large intestine. The major antibiotics associated with pseudomembranous colitis are: - Cephalosporins - Fluroquinolones - Ampicillin - Clindamycin Reference: https://medlineplus.gov/ency/article/000259.htm#:~:text=Pseudomembranous%20colitis%20refers%20to%20swelling,of%20diarrhea%20after%20antibiotic%20use. Image via: https://medtube.net/gastroenterology/medical-pictures/11390-endoscopic-appearance-of-the-pseudomembranous-colitis