title: Effect of pH and oxygen on biofilm formation in acute otitis media associated NTHi clinical isolates.
abstract: OBJECTIVE
  Biofilms occur in animal models of acute otitis media (AOM) and in children with recurrent AOM (rAOM) and chronic otitis media with effusion (OME). We therefore studied the ability of nontypeable Haemophilus influenzae (NTHi) strains from children to form biofilms in vitro under conditions we presumed occurred in the middle ear during AOM, rAOM, and OME.
  
  
  METHODS
  Evaluate NTHi isolates for biofilm formation across a pH range under aerobic, microaerophilic, and anaerobic conditions.
  
  
  METHODS
  Using a crystal violet biofilm assay we studied 12 NTHi pediatric clinical isolates to investigate biofilm formation over a pH range of 4.5 to 10 under aerobic, microaerophilic, and anaerobic conditions.
  
  
  RESULTS
  Our findings included: 1) not all clinical NTHi strains form biofilms (75% did); 2) the pH of middle ear fluid collected from AOM (n = 170; age range, 4-36 months), rAOM (n = 54; age range, 7-36 months), and OME (n = 30; age range, 9-60 months) subjects tested immediately after withdrawal was similar (mean = 8.0;range 7.0-9.0); 3) biofilms formed optimally at pH 8.0, a finding that is consistent with previous studies by other investigators; 4) biofilms did not form under aerobic conditions as likely occurs in AOM, whereas under microaerophilic and anaerobic conditions biofilm formation was observed as likely occurs during rAOM and OME.
  
  
  CONCLUSIONS
  We concluded that biofilm formation by NTHi does not occur in all strains, occurs best where the pH = 8.0 and in anaerobic conditions as likely occurs in children during rAOM and OME. However, biofilm formation is limited or absent under aerobic conditions as likely occurs during AOM.
  
  
  METHODS
  NA.
authors.affiliation: Rochester Institute of Technology, Rochester, New York.
authors.forename: Robert
authors.initials: R
authors.lastname: Osgood
authors.affiliation: Rochester Otolaryngology Group, Rochester, New York.
authors.forename: Frank
authors.initials: F
authors.lastname: Salamone
authors.affiliation: Rochester Institute of Technology, Rochester, New York.
authors.forename: Alexis
authors.initials: A
authors.lastname: Diaz
authors.affiliation: Legacy Pediatrics, Rochester, New York.
authors.forename: Janet R
authors.initials: JR
authors.lastname: Casey
authors.affiliation: Rochester Institute of Technology, Rochester, New York.
authors.forename: Peter
authors.initials: P
authors.lastname: Bajorski
authors.affiliation: Rochester General Hospital Research Institute, Rochester, New York, U.S.A.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Pichichero
mesh_terms: D000208:Acute Disease; D018441:Biofilms / Q000187:drug effects*; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006192:Haemophilus Infections / Q000378:metabolism* / Q000382:microbiology; D006193:Haemophilus influenzae / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D008297:Male; D010033:Otitis Media / Q000378:metabolism* / Q000382:microbiology; D010100:Oxygen / Q000493:pharmacokinetics*; D010101:Oxygen Consumption
chemical_list: D010100:Oxygen
keywords: Acute otitis media; anaerobic; biofilm; microaerophilic; middle ear fluid; nontypeable Haemophilus influenzae