title: Impact of polymethylmethacrylate additives on methicillin-resistant Staphylococcus pseudintermedius biofilm formation in vitro.
abstract: OBJECTIVE
  To evaluate the impact of gentamicin, silver, or both additives in polymethylmethacrylate (PMMA) beads on methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilm formation in vitro.
  
  
  METHODS
  4 preparations of PMMA beads (formed with no additive [control], gentamicin, silver, and gentamicin and silver).
  
  
  METHODS
  Beads from each group were exposed to 10 MRSP isolates known to be strong biofilm formers. Following incubation, the beads were rinsed to remove planktonic bacteria, then sonicated to dislodge biofilm-associated bacteria. Resulting suspensions were serially diluted, plated on blood agar, and incubated overnight; CFUs were counted. Variance of mean CFU counts following log10 transformation was analyzed among PMMA groups.
  
  
  RESULTS
  None of the PMMA additives tested completely inhibited MRSP biofilm formation. There was a significant effect of gentamicin and gentamicin plus silver on this variable, compared with controls, but not of silver alone. There was no difference between gentamicin and gentamicin plus silver. When only isolates not susceptible to gentamicin were evaluated, there were no significant differences among PMMA additive groups. Within gentamicin-susceptible isolates, there was an impact of gentamicin and gentamicin plus silver, but no impact of silver alone and no difference between gentamicin and gentamicin plus silver.
  
  
  CONCLUSIONS
  Gentamicin-impregnated PMMA was effective at reducing biofilm formation of gentamicin-susceptible MRSP isolates but had no effect on isolates not susceptible to gentamicin. Silver-impregnated PMMA had no effect on MRSP biofilm formation. Results suggested that gentamicin-impregnated PMMA may not be effective in vivo against MRSP isolates not susceptible to gentamicin. Antibacterial efficacy of silver should not be assumed without proper testing of the target bacteria and specific silver compound.
authors.affiliation: Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: Shauna
authors.initials: S
authors.lastname: Morrison
authors.forename: Ameet
authors.initials: A
authors.lastname: Singh
authors.forename: Joyce
authors.initials: J
authors.lastname: Rousseau
authors.forename: Meagan
authors.initials: M
authors.lastname: Walker
authors.forename: Alim
authors.initials: A
authors.lastname: Nazarali
authors.forename: Evan
authors.initials: E
authors.lastname: Crawford
authors.forename: Brigitte
authors.initials: B
authors.lastname: Brisson
authors.forename: William C
authors.initials: WC
authors.lastname: Sears
authors.forename: J Scott
authors.initials: JS
authors.lastname: Weese
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects*; D004283:Dog Diseases / Q000382:microbiology / Q000517:prevention & control*; D004285:Dogs; D005839:Gentamicins / Q000494:pharmacology; D008712:Methicillin / Q000494:pharmacology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000502:physiology*; D008863:Microspheres; D019904:Polymethyl Methacrylate / Q000494:pharmacology*; D012834:Silver / Q000494:pharmacology; D013203:Staphylococcal Infections / Q000382:microbiology / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D012834:Silver; D019904:Polymethyl Methacrylate; D008712:Methicillin