TcdB

C. difficile is a spore-forming bacterium and when the gut microbiome is perturbed by antibiotics, C. difficile spores from asymptomatic colonization or encountered through novel and frequently nosocomial exposure, can germinate into vegetative cells which can outcompete the other gut flora. Vegetative cells produce two large, secreted virulence factors, toxins A (TcdA) and B (TcdB). These two toxins can enter the epithelial cells of the colon and cause loss of intestinal membrane integrity, fluid secretion, inflammation, and cell death. TcdA and TcdB are multi-functional proteins with similar domain architecture and about 49% shared identity at the amino acid level.