Selective adherence of non-typeable Haemophilus influenzae(NTHi) to mucus or epithelial cells in the chinchilla Eustachian tube and middle ear

Abstract

Frozen sections of chinchilla Eustachian tube (ET) and middle ear mucosa were incubated with either FITC-labeled non-typeable Haemophilus influenzae(NTHi) or Bordetella pertussis. The number of bacteria adherent to “roof” vs “floor” regions was compared for each of three anatomic portions of the ET and for middle ear epithelium noting whether bacteria adhered to mucus or to epithelial cells. NTHi strains adhered significantly greater to mucus in the ET lumen whereas B. pertussispreferentially adhered to epithelial cells lining the ET ( P≤0.05). A non-fimbriated isogenic mutant of NTHi adhered significantly less to mucus than the parental isolate at all sites of the ET floor ( P≤0.05). Isolated fimbrin protein adhered to ET mucus and blocked adherence of whole organisms. Treatment with the mucolytic agent N-acetyl-L-cysteine resulted in significantly reduced adherence of NTHi to mucus ( P≤0.001) and eliminated the ability to detect binding of isolated fimbrin protein. N-acetyl-L-cysteine treatment did not affect adherence of either B. pertussisor NTHi to epithelial cells. These data indicated that NTHi may mediate ascension of the ET from the nasopharynx primarily via adherence to and growth in mucus overlying the floor region of the tubal lumen. The OMP P5-homologous fimbriae were shown to contribute to this binding.