New types of toxin A-negative, toxin B-positive strains among clinical isolates of Clostridium difficile in Australia

J Med Microbiol. 2011 Aug;60(Pt 8):1108-1111. doi: 10.1099/jmm.0.031062-0. Epub 2011 Mar 10.


A total of 817 human clinical isolates of Clostridium difficile from all Australian states were screened for A(-)B(+) strains by toxin gene PCR assays. Nine (1.1 %) strains were confirmed to be A(-)B(+) by enzyme immunoassay for toxin production. Of these, six (66.7 %) were binary toxin-positive by PCR. Using PCR ribotyping and toxinotyping, the A(-)B(+) strains could be grouped into seven ribotypes and three toxinotypes. Only one of the ribotypes had been reported previously (017). The prevalence of ribotype 017 was low in this study with only two strains detected. Two new A(-)B(+) toxinotypes were also defined (XXX, XXXI). Toxinotype XXX had a toxin B gene similar to that of toxinotype IV (A(+)B(+)) but with a novel cytopathic region. Toxinotype XXXI was similar to other A(-)B(+) types (X, XVII), but had a larger deletion to the toxin A gene than in either of those types. The types of A(-)B(+) strains identified in this study differed markedly from those described in other regions.

MeSH terms

  • Australia / epidemiology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Bacterial Toxins / genetics
  • Bacterial Toxins / metabolism*
  • Clostridium Infections / epidemiology
  • Clostridium Infections / microbiology*
  • Clostridium difficile / classification
  • Clostridium difficile / genetics
  • Clostridium difficile / metabolism*
  • Enterotoxins / genetics
  • Enterotoxins / metabolism*
  • Gene Expression Regulation, Bacterial
  • Humans
  • Polymerase Chain Reaction
  • Ribotyping


  • Bacterial Proteins
  • Bacterial Toxins
  • Enterotoxins
  • tcdA protein, Clostridium difficile
  • toxB protein, Clostridium difficile