Clostridioides difficile toxin A (TcdA), Clostridioides difficile toxin B (TcdB), and Clostridioides difficile binary toxin (CDT); also includes Clostridioides difficile surface layer protein A (SlpA) (TcdA, TcdB, CDT (for toxins); SlpA (for surface layer))

Clostridioides difficile antigens refer to a variety of immunologically relevant proteins produced by the Gram-positive, anaerobic bacterium C. difficile. Most importantly, this includes the large exotoxins—TcdA (toxin A) and TcdB (toxin B)—which are responsible for the majority of host cell injury in C. difficile infection. These toxins act by glucosylating Rho GTPases, disrupting the actin cytoskeleton, cell-cell junctions, and inducing apoptosis and inflammatory signaling. Some strains also produce binary toxin (CDT), an ADP-ribosyltransferase acting primarily on actin. Additionally, S-layer protein A (SlpA) forms a paracrystalline surface coat on the bacterium that is essential for host interactions and is a potential vaccine and diagnostic antigen. Therapeutic targeting of these antigens—primarily via antibody-mediated toxin neutralization (e.g., bezlotoxumab)—is an established approach for prevention and mitigation of recurrent C. difficile infection. However, the term "C. difficile antigens" is scientifically ambiguous without specifying the exact protein, as it can refer to diverse structural or secreted molecules with highly distinct functions and relevance.

Other names

C. difficile toxinsC. difficile S-layer proteinsCD toxin ACD toxin Bbinary toxinS-layer protein

Neutralization of toxins (antibodies/antitoxin drugs bind TcdA or TcdB to prevent cell entry and cytotoxicity). Inhibit toxin-receptor interactions (monoclonal antibodies). Reduce toxin-mediated epithelial damage. Antibiotics: kill *C. difficile* bacteria, eliminating antigen production.