A Hospital Outbreak of Clostridium Difficile Disease Associated With Isolates Carrying Binary Toxin Genes

Clin Infect Dis. 2005 Jan 15;40(2):265-72. doi: 10.1086/427113. Epub 2004 Dec 15.


Introduction: The binary toxin genes cdt and cdtB have been detected in approximately 5% 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 >or=2 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 (P=.23). Severity of CDD was not associated with either severe underlying disease or comorbid conditions. The strains that caused severe CDD belonged to 4 protein profile groups and >or=3 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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • ADP Ribose Transferases / genetics
  • Adult
  • Aged
  • Aged, 80 and over
  • Bacterial Proteins / genetics
  • Bacterial Toxins / genetics*
  • Clostridium difficile / classification
  • Clostridium difficile / genetics*
  • Clostridium difficile / isolation & purification
  • Cross Infection / microbiology*
  • Disease Outbreaks*
  • Enterocolitis, Pseudomembranous / microbiology
  • Humans
  • Middle Aged
  • Retrospective Studies


  • Bacterial Proteins
  • Bacterial Toxins
  • ADP Ribose Transferases
  • actin-specific ADP-ribosyltransferase, Clostridium