title: PCR-based detection of bacterial DNA after antimicrobial treatment is indicative of persistent, viable bacteria in the chinchilla model of otitis media.
abstract: OBJECTIVE
  Bacterial deoxyribonucleic acid (DNA) has been previously detected by polymerase chain reactions (PCR) in a significant percentage of culturally-sterile pediatric middle-ear effusions. The current study was designed to determine whether this represents the existence of viable bacteria or the persistence of residual DNA in the middle-ear cleft.
  
  
  METHODS
  The middle-ear cavities of two sets of chinchillas were inoculated with either: 1) 100 colony-forming units (CFU) of live Haemophilus influenzae, 2.2 x 10(6) CFU of pasteurized Moraxella catarrhalis, and 1000 ng of DNA (>10(8) genomic equivalents) from Streptococcus pneumoniae; or 2) 100 CFU of live S pneumoniae, 2.2 x 10(6) CFU of pasteurized M catarrhalis and 1000 ng of purified DNA from H influenzae. Animals were treated with ampicillin for 5 days beginning on day 3. A single-point longitudinal study design was used for sampling to eliminate the possibility of contamination.
  
  
  RESULTS
  No DNA was detectable from the heat-killed bacteria or the purified DNA after day 3. However, DNA from the live bacteria persisted through day 21, even though all specimens were culture-negative following the initiation of antimicrobial therapy.
  
  
  CONCLUSIONS
  These findings indicate that purified DNA and DNA from intact but nonviable bacteria do not persist in the middle-ear cleft in the presence of an effusion, even following high copy inoculation. In contrast, antibiotic-treated bacteria persist in some viable state for weeks as evidenced by the differential ability of the PCR-based assay systems to detect the live bacteria, but not detect the heat-killed organisms.
authors.affiliation: Department of Pathology, School of Medicine, University of Pittsburgh Medical Center, Pennsylvania 15261, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Post
authors.forename: J J
authors.initials: JJ
authors.lastname: Aul
authors.forename: G J
authors.initials: GJ
authors.lastname: White
authors.forename: R M
authors.initials: RM
authors.lastname: Wadowsky
authors.forename: T
authors.initials: T
authors.lastname: Zavoral
authors.forename: R
authors.initials: R
authors.lastname: Tabari
authors.forename: B
authors.initials: B
authors.lastname: Kerber
authors.forename: W J
authors.initials: WJ
authors.lastname: Doyle
authors.forename: G D
authors.initials: GD
authors.lastname: Ehrlich
mesh_terms: D000667:Ampicillin / Q000627:therapeutic use*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D002682:Chinchilla; D004269:DNA, Bacterial; D006193:Haemophilus influenzae / Q000472:pathogenicity*; D001936:Moraxella catarrhalis / Q000472:pathogenicity*; D010033:Otitis Media / Q000188:drug therapy / Q000209:etiology / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods*; D013296:Streptococcus pneumoniae / Q000472:pathogenicity*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D000667:Ampicillin