Production of actin-specific ADP-ribosyltransferase (binary toxin) by strains of Clostridium difficile

In addition to the two large clostridial cytotoxins (TcdA and TcdB) certain strains of Clostridium difficile produce an actin-specific ADP-ribosyltran sferase, or binary toxin. PCR reactions were developed to detect genes enco ding the enzymatic (cdtA) and binding (cdtB) components of the binary toxin and 170 representative strains were tested to assess the prevalence of the toxin. Positive PCR results (n = 59) were confirmed by immunoblotting and ADP-ribosyltransferase assay. PCR ribotype and toxinotype (restriction frag ment length polymorphism analysis of genes for TcdA and TcdB) correlated wi th possession of binary toxin genes. All strains with cdtA and cdtB belonge d to toxin-variable toxinotypes and five toxin-producing groups of strains have been described according to the presence or absence of TcdA. TcdB and binary toxin. Result indicate that ca. 6.4% of toxigenic isolates of C. dif ficile referred to the Anaerobe Reference Unit from UK hospitals have cdtA and cdtB genes. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.