[Pseudomembraneous colitis caused by a toxin B-positive and a toxin A-negative strain of Clostridium difficile].

We describe a case of pseudomembraneous colitis (PMC) caused by a toxin A- B+ strain of Clostridium difficile (CD). In Denmark only a few laboratories investigate for toxin production, and if they do, the toxin A enzyme immunoassay (EIA) is the test generally used when testing for CD. This toxin A negative but toxin B positive strain thus remains undetectable. If CD-associated diarrhea is clinically suspected and tests for toxin A are negative, infection with a toxin A- B+ strain should be considered. Further diagnostic tests such as cellular cytotoxicity assays or toxin A/B EIA should be performed. The standard treatment of PMC in severely ill patients should be vancomycin, administered orally.