pathology

Last reviewed 07/2021

Pseudomembranous colitis is associated with the administration of broad spectrum antibiotics, leading to the death of the normal bacteria in the gut and the growth of Clostridium difficile.

Pathogenic strains of C. difficile produce toxins that cause diarrhoea and colitis. Strains of C. difficile which do not produce toxins are not pathogenic. The two toxins produced by C. difficile are toxin A, a 308-kd enterotoxin, and toxin B, a 250-270-kd cytotoxin. The intracellular mechanisms of action of these two toxins are poorly understood; toxin B is approximately 1000x as powerful as toxin A.

There is the formation of a thick, fibrinous blanket of 'pseudomembrane' over the colonic surface as a result of intense inflammation. This pseudomembrane harbours the proliferating Clostridium difficile allowing them to continue to produce toxin.