title: Biofilm-forming skin microflora bacteria are resistant to the bactericidal action of disinfectants used during blood donation.
abstract: BACKGROUND
  A one-step skin disinfection method containing 2% chlorhexidine-gluconate (CHG) and 70% isopropyl alcohol (IPA) is currently used by blood suppliers worldwide. Reports of bacterially contaminated platelet concentrates (PCs) indicate that skin disinfection is not fully effective. Approximately 20% of skin microflora exist as surface-attached aggregates (biofilms), known for displaying increased resistance to disinfectants. This study was aimed at determining whether skin microflora biofilm-positive Staphylococcus epidermidis and Staphylococcus capitis are resistant to CHG and/or IPA.
  
  
  METHODS
  Free-floating cells and mono or dual (1 : 1 ratio) biofilms of S. epidermidis and S. capitis were exposed to CHG, IPA, or CHG/IPA for 30 seconds, simulating skin disinfection practices. Residual viable cells were quantified by colony counting. Morphology of disinfectant-treated S. epidermidis biofilms was examined by scanning electron microscopy. Treated S. epidermidis and S. capitis biofilms were inoculated into PCs and bacterial concentrations were determined on Days 0 and 5 of storage.
  
  
  RESULTS
  Treatment of staphylococcal biofilm cells with all disinfectants caused cell damage and significant reduction in viability, with CHG/IPA being the most effective. However, biofilms were significantly more resistant to treatment than free-floating cells. Disinfectant-treated S. epidermidis proliferated better in PCs than S. capitis, especially when grown as monospecies biofilms.
  
  
  CONCLUSIONS
  Although CHG/IPA is effective in reducing the viability of S. epidermidis and S. capitis biofilms, these organisms are not completely eliminated. Furthermore, disinfectant-treated staphylococcal biofilms multiply well in PCs. These results demonstrate that the biofilm-forming capability of the skin microflora reduces the bactericidal efficiency of blood donor skin disinfectants.
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Mariam
authors.initials: M
authors.lastname: Taha
authors.forename: Miloslav
authors.initials: M
authors.lastname: Kalab
authors.forename: Qi-Long
authors.initials: QL
authors.lastname: Yi
authors.forename: Carey
authors.initials: C
authors.lastname: Landry
authors.forename: Valerie
authors.initials: V
authors.lastname: Greco-Stewart
authors.forename: Ann Karen
authors.initials: AK
authors.lastname: Brassinga
authors.forename: Costi D
authors.initials: CD
authors.lastname: Sifri
authors.forename: Sandra
authors.initials: S
authors.lastname: Ramirez-Arcos
mesh_terms: D019840:2-Propanol; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D018441:Biofilms / Q000254:growth & development*; D001782:Blood Donors; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D006801:Humans; D012867:Skin / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000502:physiology*
chemical_list: D000891:Anti-Infective Agents, Local; C010882:chlorhexidine gluconate; D019840:2-Propanol; D002710:Chlorhexidine