Deletions in the repeating sequences of the toxin A gene of toxin A-negative, toxin B-positive Clostridium difficile strains

The repeating sequences of the toxin A gene from toxin A-negative, toxin B- positive (toxin A-, toxin B+) strains of Clostridium,difficile which were i solated in geographically separated facilities in Japan and Indonesia were determined. All six strains tested had identical repeating sequences with t wo deletions (1548 and 273 nucleotides in size) in the toxin A gene. A PCR method was designed to detect the deletions and the deletions were confirme d in all 50 toxin A-, toxin B+ strains examined by this method. Western imm unoblot analysis revealed that polyclonal antiserum against native toxin A did not react with the concentrated. culture filtrates of the toxin A-, tox in B+ strains. These resulrs may suggest that toxin A-, toxin B+ strains ha ve deletions of the two thirds of the repeating regions of the toxin A gene , which encodes the epitopes fully responsible for the reaction with the po lyclonal antiserum. (C) 1999 Federation of European Microbiological Societi es. Published by Elsevier Science B.V. All rights reserved.