title: Dental unit water treatment with hydrogen peroxide and monovalent silver ions artificially contaminated with freshly isolated pathogens.
abstract: BACKGROUND
  Dental unit water (DUW) could be contaminated by human pathogens coming from biological fluids penetrated during patient treatment and by opportunistic pathogens detached from aquatic biofilm. These microorganisms could be spread to following patients. We tested the disinfectant activity of hydrogen peroxide and monovalent silver ions (H(2)O(2)-Ag(+)) into DUW artificially contaminated with freshly isolated pathogens.
  
  
  METHODS
  The tested microorganisms were Staphylococcus aureus, Enterococcus faecalis, Candida albicans, Pseudomonas aeruginosa, Legionella pneumophila, Mycobacterium chelonae, non-pathogenic Bacillus clausii spores. Bacterial suspensions were inoculated into the waterlines of pre-sterilized dental turbines. The test-turbines were connected to DUW and contaminated water was treated for 10 minutes with H(2)O(2)-Ag(+)-based disinfectant (H(2)O(2) 3% v/v, Ag(+) 0.001% w/v). The control-turbines were left untreated. Turbines were washed with sterile hard water used to assess the residual bacterial loads (expressed in colony forming units -cfu). Each strain was tested five times and the mean log loads were assessed. Following the European Standardization Committee, the disinfectant activity was evaluated as mean log load reduction, that is, the difference between the mean log load detected on the control-turbines and the mean log load detected on the test-turbines.
  
  
  RESULTS
  Mean bacterial loads detected on the control-turbines ranged between 105-107 cfu. The mean log load reductions resulted 7.5 log cfu for S. aureus, E. faecalis, P. aeruginosa, 6.3 for C. albicans, 5.4 for L. pneumophila, 5.3 for M. chelonae, 2.9 for B. clausii spores.
  
  
  CONCLUSIONS
  DUW disinfection with H(2)O(2)-Ag(+) could help minimize the risk that planktonic pathogens are spread to patients during dental treatment.
authors.affiliation: Department of Public Health and Infectious Diseases, Sapienza University, Rome, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Petti
authors.affiliation: Department of Dental and Maxillofacial Sciences, Sapienza University, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Polimeni
authors.affiliation: Water Research Foundation (retired), Denver, CO, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Allen
mesh_terms: D015169:Colony Count, Microbial; D019551:Dental Disinfectants / Q000494:pharmacology*; D003748:Dental Equipment / Q000382:microbiology*; D004203:Disinfection / Q000379:methods; D017408:Guidelines as Topic; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D019552:Infection Control, Dental / Q000379:methods; D012834:Silver / Q000494:pharmacology*; D014871:Water Microbiology
chemical_list: D019551:Dental Disinfectants; D012834:Silver; D006861:Hydrogen Peroxide
keywords: Cross infection; Dental unit water; Hydrogen peroxide; Silver ions