Enzyme immunoassay for detection of Clostridium difficile toxins A and B in patients with antibiotic-associated diarrhoea and colitis.

A sandwich enzyme immunoassay (ELISA) was developed to detect Clostridium difficile toxins A and B in stools from patients with antibiotic associated diarrhoea and colitis. Immune serum to crude Clostridium difficile toxin and non-immune serum were coated onto polystyrene microtiter plates to act as capture antibodies; toxins A and B in human stools were detected by antibodies from rabbits immunized with purified toxins A and B. The ELISA for toxin B showed cross-reactions with Clostridium bifermentans and Clostridium sordellii and lacked diagnostic sensitivity in clinical samples. The ELISA for toxin A showed no cross-reactions with other clostridiae investigated and was positive in 33% (62/189) of patients with antibiotic associated diarrhoea. This compared with 38% (71/189) positive in the tissue culture assay for Clostridium difficile cytotoxin. With a predictive value of 96% in clinical specimens, the ELISA for toxin A constitutes a sensitive and specific tool for diagnosis of Clostridium difficile associated diarrhoea and colitis.