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  • Expression of the cytolethal distending toxin in a geographically diverse collection of Haemophilus ducreyi clinical isolates

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Original articles
Expression of the cytolethal distending toxin in a geographically diverse collection of Haemophilus ducreyi clinical isolates
  1. K Kulkarni1,
  2. D A Lewis1,2,
  3. C A Ison1
  1. 1Department of Infectious Diseases and Microbiology, Faculty of Medicine, Imperial College, London W2 1PG, UK
  2. 2Department of Microbiology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75235-9048, USA
  1. Correspondence to:
    Dr C A Ison, Department of Infectious Disease and Microbiology, Faculty of Medicine, Imperial College London, St Mary’s Campus, Norfolk Place, London W2 1PG, UK;
    c.ison{at}ic.ac.uk

Abstract

Objective: To screen a collection of isolates of Haemophilus ducreyi for expression of the cytolethal distending toxin (CDT).

Methods: 45 clinical isolates of H ducreyi were screened for cytotoxic activity by examining the effect of culture supernatants on Hela cells. Expression was confirmed using immunoblotting with CDT specific monoclonal antibodies and the presence of the cdt genes determined by amplification of the cdt genes in a multiplex polymerase chain assay.

Results: Of the 45 clinical isolates, six isolates from differing geographical origins did not demonstrate cytotoxic activity. Expression of CDT was also not detected in these six isolates using immunoblotting and the genes cdtA, cdtB, and cdtC were not amplified using PCR. The remaining isolates demonstrated cytotoxic activity, expressed the CDT proteins, and the presence of the cdt genes was confirmed.

Conclusions: CDT is considered a virulence factor of H ducreyi but was found to be absent in 13% of isolates from different geographical origins.

  • cytolethal distending toxin
  • Haemophilus ducreyi
  • chancroid

https://doi.org/10.1136/sti.79.4.294

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