The use of systemic antibiotics, including broad-spectrum penicillins/cephalosporins, fluoroquinolones, and clindamycin, causes the normal microbiota of the bowel to be altered. In particular, when the antibiotic kills off other competing bacteria in the intestine, any bacteria remaining will have less competition for space and nutrients. The net effect is to permit more extensive growth than normal of certain bacteria. C.<unk>  is one such type of bacterium. In addition to proliferating in the bowel, C.<unk>  also produces toxins. Without either toxin A or toxin B, C.<unk>  may colonize the gut, but is unlikely to cause pseudomembranous colitis. The colitis associated with severe<unk>  is part of an inflammatory reaction, with the "pseudomembrane" formed by a viscous collection of inflammatory cells, fibrin, and necrotic cells.
Clostridioides difficile infection
Antibiotic-associated diarrhea
Irritable bowel syndrome
Campylobacteriosis
Gay bowel syndrome
Wilderness-acquired diarrhea
Factitious diarrhea
Cytomegalovirus colitis