Most often, pseudomembranous colitis develops under the influence of long-term use of antibiotics ampicillin, lincomycin, clindamycin, cephalosporins, less often - penicillin, erythromycin, chloramphenicol, tetracycline. Clostridium difficile is a spore-forming gram-positive anaerobic rod that is capable of producing two types of exotoxins: toxin A and toxin B. There are four main causes of pseudomembranous colitis associated with C. difficile.