title: Antibacterial activity of retinaldehyde against Propionibacterium acnes.
abstract: BACKGROUND
  Retinaldehyde has been shown to exert antibacterial activity in vitro.
  
  
  OBJECTIVE
  This study evaluates the effect of retinaldehyde on Propionibacterium acnes both in vivo and in vitro.
  
  
  METHODS
  Microbial minimal inhibitory concentrations (MICs) of retinaldehyde and retinoic acid were determined on reference strains of P. acnes. In vivo activity of daily topical application of 0.05% retinaldehyde on the P. acnes density was evaluated after application in a single-blind randomised study.
  
  
  RESULTS
  MICs of retinaldehyde were 4 mg/l for P. acnes No. CIP179 and CIP53119 and 8 mg/l for P. acnes No. CIP53117. In contrast, the MICs of retinoic acid were superior to 128 mg/l for these three strains. In vivo, retinaldehyde-treated areas displayed a significant decrease in counts of viable P. acnes as compared with the untreated areas with a median decrease of 10(2) log P. acnes/cm(2) after 2 weeks of daily application. Vehicle alone had no effect.
  
  
  CONCLUSIONS
  The MIC of retinaldehyde against P. acnes suggests a direct antibacterial activity. Daily topical application of 0.05% retinaldehyde is associated with a clear reduction of the P. acnes density.
authors.affiliation: Department of Dermatology, Geneva University Hospital, Geneva, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Pechère
authors.forename: J C
authors.initials: JC
authors.lastname: Pechère
authors.forename: G
authors.initials: G
authors.lastname: Siegenthaler
authors.forename: L
authors.initials: L
authors.lastname: Germanier
authors.forename: J H
authors.initials: JH
authors.lastname: Saurat
mesh_terms: D000287:Administration, Topical; D006801:Humans; D008826:Microbial Sensitivity Tests; D011425:Propionibacterium acnes / Q000187:drug effects* / Q000254:growth & development; D012172:Retinaldehyde / Q000494:pharmacology*; D016037:Single-Blind Method; D012867:Skin / Q000382:microbiology*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D014212:Tretinoin; D012172:Retinaldehyde