title: Systemic reactivation of otitis media with effusion in a rat model.
abstract: OBJECTIVE
  This study addresses the interaction of bacterial antigens, specifically peptidoglycan-polysaccharide (PG-PS) and lipopolysaccharide (LPS), in the induction and reactivation of mucoid middle ear effusions.
  
  
  METHODS
  Twenty-seven rats underwent eustachian tube obstruction before inoculation of the middle ear bulla with PG-PS. Three weeks later, after resolution of all middle ear effusions, 6 rats were randomly selected and euthanized as the first control group (control I). The remaining 21 animals were randomly assigned to 3 groups that received intravenous injections of Krebs Ringer (control II), PG-PS, and LPS, respectively. These rats were euthanized 2 days after intravenous injection. Middle ear mucin production and histologic changes were measured in all animals.
  
  
  RESULTS
  The mean concentrations of mucin were 0.94 +/- 0.52 mg/mL, 0.41 +/- 0.87 mg/mL, 16.33 +/- 3.67 mg/mL, and 1.15 +/- 0.41 mg/mL in the control I, control II, PG-PS, and LPS groups, respectively. Thus the mean concentration of mucin in the middle ear lavage samples was significantly greater in rats that were injected intravenously with PG-PS than in rats in other groups (P < 0.05). Histologic analyses demonstrated a greater degree of goblet cell hyperplasia in the PG-PS group than in other groups.
  
  
  CONCLUSIONS
  This is the first animal model of recurring otitis media with effusion in which a systemic injection of PG-PS was used to reactivate a middle ear effusion in rats previously primed with a transtympanic injection of PG-PS. This study suggests that after otitis media with effusion has resolved, it may be reactivated by the presence of bacterial antigens and/or cytokines in the systemic circulation.
authors.affiliation: Division of Otolaryngology Head and Neck Surgery, Department of Surgery, University of Chapel Hill, School of Medicine, North Carolina 27599-7070, USA.
authors.forename: B S
authors.initials: BS
authors.lastname: Jewett
authors.forename: J P
authors.initials: JP
authors.lastname: Prazma
authors.forename: S E
authors.initials: SE
authors.lastname: Hunter
authors.forename: A S
authors.initials: AS
authors.lastname: Rose
authors.forename: J M
authors.initials: JM
authors.lastname: Clark
authors.forename: B R
authors.initials: BR
authors.lastname: Sartor
authors.forename: H C
authors.initials: HC
authors.lastname: Pillsbury
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000502:physiology*; D016207:Cytokines / Q000502:physiology*; D004195:Disease Models, Animal; D005069:Evaluation Studies as Topic; D008070:Lipopolysaccharides / Q000494:pharmacology*; D010034:Otitis Media with Effusion / Q000473:pathology / Q000503:physiopathology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012008:Recurrence
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; D008070:Lipopolysaccharides