title: Disruption of nasopharyngeal epithelium by pneumococci is density-linked.
abstract: BACKGROUND
  The aim of this project was to study the influence of pneumococci on nasopharyngeal epithelial integrity as a function of time and pneumococcal density.
  
  
  METHODS
  Cell layers of an in vitro model of human nasopharyngeal epithelium were inoculated with different pneumococcal strains. The transepithelial electrical resistance (TEER), a measure of the integrity of the cell layers, and the pneumococcal concentration in the apical fluid on the epithelial cells were measured at different times after inoculation.
  
  
  RESULTS
  Pneumococci caused a decrease in the TEER when a density of 1 x 107 CFU mL-1 was reached. The growth rate of pneumococci in our in vitro model differed between the strains tested and, for the same strain, between in vitro culture on the epithelial cells and broth culture. Differences in timing of the onset of decrease in the TEER between strains were the result of differences in growth rate on the epithelial cells. Antibiotic-induced lysis of pneumococci caused an immediate decrease in the TEER of the cell layers.
  
  
  CONCLUSIONS
  Pneumococci cause a decrease in the TEER at a density of 1 x 107 CFU mL-1. Our hypothesis is that this decrease in the TEER is the result of quorum-induced lysis of the pneumococci.
authors.affiliation: Rega Institute Department of Microbiology, UZ Gasthuisberg, Leuven, Belgium. katrien.lagrou@uz.kuleuven.ac.be
authors.forename: K
authors.initials: K
authors.lastname: Lagrou
authors.forename: W E
authors.initials: WE
authors.lastname: Peetermans
authors.forename: J
authors.initials: J
authors.lastname: Verhaegen
authors.forename: M
authors.initials: M
authors.lastname: Jorissen
authors.forename: J
authors.initials: J
authors.lastname: Van Eldere
mesh_terms: D017097:Electric Impedance; D004848:Epithelium / Q000382:microbiology; D006801:Humans; D066298:In Vitro Techniques; D008854:Microscopy, Electron / Q000379:methods; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000382:microbiology*; D013296:Streptococcus pneumoniae