The PilA protein of non-typeable Haemophilus influenzae plays a role in biofilm formation, adherence to epithelial cells and colonization of the mammalian upper respiratory tract

Mol Microbiol. 2007 Sep;65(5):1288-99. doi: 10.1111/j.1365-2958.2007.05864.x. Epub 2007 Jul 23.


We recently described the expression of type IV pili (Tfp) by non-typeable Haemophilus influenzae (NTHI), a common respiratory tract pathogen. Prior to that report, Tfp were not thought to be produced by NTHI as they are not observed on NTHI when grown on chocolate agar or other commonly used growth media. To further characterize growth conditions permissive for the expression of NTHI Tfp, as well as determine their role in colonization and virulence, we transformed an NTHI otitis media isolate with a reporter plasmid containing the lux gene cluster driven by the pilA promoter. Transcription from the pilA promoter was demonstrated under a variety of in vitro growth conditions and, importantly, by ex vivo imaging of luciferase-producing NTHI in infected chinchillas. Luciferase-producing NTHI were also identified within a biofilm formed by NTHI in vivo. We further demonstrated a role for NTHI PilA in adherence to human respiratory epithelial cells, in colonization of the chinchilla respiratory tract as well as a requirement for PilA in biofilm development, both in vitro and in vivo. Collectively, our data demonstrate that NTHI express PilA in vivo, and that PilA plays an important role in the pathogenesis of an upper respiratory tract infection induced by NTHI.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Animals
  • Bacterial Adhesion / physiology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biofilms*
  • Chinchilla / anatomy & histology
  • Chinchilla / microbiology
  • Ear, Middle / microbiology
  • Epithelial Cells / microbiology*
  • Fimbriae, Bacterial / metabolism
  • Gene Expression Regulation, Bacterial
  • Haemophilus Infections*
  • Haemophilus influenzae* / genetics
  • Haemophilus influenzae* / metabolism
  • Haemophilus influenzae* / pathogenicity
  • Humans
  • Multigene Family
  • Promoter Regions, Genetic
  • Respiratory System* / cytology
  • Respiratory System* / microbiology


  • Bacterial Proteins