title: An effective method of inactivating chlorhexidine.
abstract: OBJECTIVE
  The purpose of this study was to find an effective inactivating agent for chlorhexidine that would facilitate removal of all residual antimicrobial effect, which may cause false-negative results during microbiologic culturing.
  
  
  METHODS
  L-alpha-lecithin, Tween 80, and sodium thiosulfate were used in different proportions to prepare 6 potential inactivating solutions. Nine mL of each inactivating solution was mixed with 1 mL of 2% chlorhexidine solution. After 5 minutes of equilibration, 0.1 mL of bacterial cell suspension containing 2 x 10(4) viable cell of Enterococcus faecalis was added to the mixture. At 10 and 60 minutes, 0.1-mL aliquots were withdrawn and spread over blood agar plates and incubated at 37 degrees C for 72 hours. The number of colony-forming units on the blood agar plates was determined and recorded.
  
  
  RESULTS
  The combination of 3% Tween 80 and 0.3% L-alpha-lecithin was found to be the most effective inactivating agent, allowing full recovery of the test organisms in the presence of chlorhexidine.
  
  
  CONCLUSIONS
  The present study demonstrated a method to predictably inactivate chlorhexidine.
authors.affiliation: University of Connecticut, Farmington, Conn 06030, USA. zamanya@hotmail.com
authors.forename: Ahmad
authors.initials: A
authors.lastname: Zamany
authors.forename: Larz S W
authors.initials: LS
authors.lastname: Spångberg
mesh_terms: D000891:Anti-Infective Agents, Local / Q000037:antagonists & inhibitors*; D000975:Antioxidants / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D002710:Chlorhexidine / Q000037:antagonists & inhibitors*; D015169:Colony Count, Microbial; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D008422:Materials Testing; D010713:Phosphatidylcholines / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D012388:Root Canal Irrigants; D013501:Surface-Active Agents / Q000494:pharmacology; D013885:Thiosulfates / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000891:Anti-Infective Agents, Local; D000975:Antioxidants; D002614:Chelating Agents; D010713:Phosphatidylcholines; D011136:Polysorbates; D012388:Root Canal Irrigants; D013501:Surface-Active Agents; D013885:Thiosulfates; C017717:sodium thiosulfate; D002710:Chlorhexidine