A pilus-deficient mutant of Haemophilus ducreyi is virulent in the human model of experimental infection

Jaffar A. Al-Tawfiq, Margaret E. Bauer, Kate R. Fortney, Barry P. Katz, Antoinette F. Hood, Margaret Ketterer, Michael A. Apicella, Stanley M. Spinola

Research output: Contribution to journalArticle

19 Scopus citations


Haemophilus ducreyi expresses fine tangled pili, which are composed predominantly of a major subunit (FtpA). Confocal microscopy showed that an FtpA-specific monoclonal antibody bound to bacteria in biopsy samples obtained from infected human volunteers. To test the role of pill in pathogenesis, an isogenic mutant (35000HP-SMS1) was constructed by insertionally inactivating ftpA. 35000HP-SMS1 did not express FtpA and was nonpiliated but was otherwise identical to its parent, 35000HP. Seven healthy adults were challenged on the upper arm with the isogenic isolates in a double-blinded, escalating dose-response study. Sites inoculated with the mutant produced papules and pustules at rates similar to the rates observed at sites inoculated with the parent. The recovery rate of H. ducreyi from cultures and the histopathology of biopsy samples obtained from pustules inoculated with 35000HP or 35000HP-SMS1 were similar. Although pili are expressed in vivo, FtpA is not required for pustule formation in the human challenge model.

Original languageEnglish (US)
Pages (from-to)1176-1179
Number of pages4
JournalJournal of Infectious Diseases
Issue number3
StatePublished - Apr 19 2000


ASJC Scopus subject areas

  • Immunology and Allergy
  • Infectious Diseases

Cite this