Haemophilus ducreyi Requires an Intact flp Gene Cluster for Virulence in Humans

Stanley M. Spinola, Kate R. Fortney, Barry P. Katz, Jo L. Latimer, Jason R. Mock, Merja Vakevainen, Eric J. Hansen

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


An intact Haemophilus ducreyi flp operon is essential for microcolony formation in vitro. tadA is the 9th of 15 genes in the operon and has homology to NTPases of type IV secretion systems. Fifteen human volunteers were experimentally infected with both H. ducreyi 35000HP and the tadA mutant, 35000HP.400. Papules developed at similar rates at sites inoculated with the mutant and parent, while pustules formed at 36.4% of parent sites and at 0% of mutant sites (P = 0.001). Compared to 35000HP, 35000HP.400 had only a modest but significant reduction in lesion scores in the temperature-dependent rabbit model of chancroid. These data suggest that proteins secreted by the flp locus are required for full expression of virulence by H. ducreyi in humans but have less of a role in virulence in an animal model of infection.

Original languageEnglish (US)
Pages (from-to)7178-7182
Number of pages5
JournalInfection and immunity
Issue number12
StatePublished - Dec 2003

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases


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