Characterization of cross-reactive proteins detected by Culturette Brand Rapid Latex Test for Clostridium difficile.

Clostridium sporogenes, Peptostreptococcus anaerobius, and Bacteroides asaccharolyticus have been reported to react in the Culturette Brand Rapid Latex Test (Marion Scientific, Div. Marion Laboratories, Inc., Kansas City, Mo.) for Clostridium difficile. From the results of this study we showed that C. sporogenes and P. anaerobius produce a protein which is very similar biochemically and immunologically to the protein of C. difficile that is detected by the test. Thus, the positive latex reactions observed with C. sporogenes and P. anaerobius are due to a cross-reactive protein. We did not detect this cross-reactive protein in filtrates from B. asaccharolyticus, indicating that this bacterium reacts with the latex reagent by some other mechanism. We cloned the C. difficile gene that codes for the cross-reactive protein and showed that the protein produced by the recombinant organism is nontoxic and distinct from toxin A, thus confirming our earlier findings.