Development of an ELISA kit using monoclonal antibody to Clostridium difficile toxin A

AIM: To establish an ELISA kit using monoclonal antibodiesagainst Clostridium difficile ( C. difficile) toxin A.METHODS: An indirect sandwich ElISA was described using the purified rabbit monospecific antiserum as capturing antibody. After the polystyrene microtitre plates with 96 fiat-bottomed wells were coated with rabbit antiserum, the wells were blocked with 100 g/L BSA in PBS-T. C. difficiletoxin A or culture filtrates were added to each well and then monoclonal antibodies IgG-horseradish peroxidase conjugate was added as detecting antibody, tetramethylbenzidine was used as substrate and A450 of the stopped reacting product was recorded in an automated plate reader. RESULTS: The tested specimens included culture filtrates of 2 strains of toxigenic C. difficile, 2 strains of non-toxigenic C. difficile, 26 strains of E. coli, 2 strains of S. dysenteriae, 1 strain of Bif infantis, 5 strains of V. cholera, 2 strains ofS. typhi, 7 strains of C. botulinum, 1 strain of toxigenic C. sordllii, and 1 strain of C. butyricum. A total of 47 strains of culture filtrates were all negative except for 2 strains of toxigenic C. difficile. The detective limitation of toxin A was 0.1 ng/mL.CONCLUSION: An ELISA kit with high specificity and excellent sensitivity for the rapid detection of C. difficile toxin A was established. It will be a useful tool for diagnostic test of C. difficile toxin A.