A hospital outbreak of Clostridium difficile disease associated with isolates carrying binary toxin genes

Introduction. The binary toxin genes cdt and cdtB have been detected in similar to5% of Clostridium difficile strains. Severe C. difficile disease ( CDD) may be associated with strains that carry the binary toxin genes. Methods. From April 2001 through March 2002, 8 severe and 41 nonsevere cases of nosocomial CDD were studied. Severe cases of CDD were defined by the presence of greater than or equal to2 of the following criteria: ( 1) abdominal pain, ( 2) a white blood cell count of >20,000 or <1500 cells/mm(3), and ( 3) ileus or bowel wall thickening with ascites. Underlying disease was assessed by 2 methods: a modified Horn score and the presence of comorbid conditions. The presence of cdtA, cdtB, and the toxin A and toxin B genes was determined, and molecular subtyping was performed. Results. All strains were positive for the toxin A and B genes, and 65.3% of the strains carried the cdtA and cdtB genes. Strains that carried the binary toxin genes accounted for 87.5% of the cases of severe CDD and 61.0% of the nonsevere cases (). Severity of CDD was not associated with either severe underlying disease or Pp. 23 comorbid conditions. The strains that caused severe CDD belonged to 4 protein profile groups and greater than or equal to3 restriction endonuclease analysis ( REA) groups. All ( i.e., 5 of 5) strains in REA group BI, compared with none ( i.e., 0 of 7) of the strains in REA group J carried the binary toxin genes (P=.001). Strains that belonged to REA groups BK and BR also carried the binary toxin genes. Conclusions. The binary toxin genes were present in nearly two-thirds of the C. difficile strains, and they were correlated with the REA group. Severity of CDD was not closely associated with a specific clone or underlying disease, but it may be associated with the presence of the binary toxin genes. Larger studies are needed to discern whether a true association exists and whether the binary toxin alters the pathogenicity of the C. difficile strain.