Endodontics| Volume 93, ISSUE 5, P617-620, May 2002

An effective method of inactivating chlorhexidine


      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. Study Design. L-α-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 × 104 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 At 10 and 60 minutes, 0.1-mL aliquots were withdrawn and spread over blood agar plates and incubated at 37°C for 72 hours.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-α-lecithin was found to be the most effective inactivating agent, allowing full recovery of the test organisms in the presence of chlorhexidine. Conclusion. The present study demonstrated a method to predictably inactivate chlorhexidine. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:617-20)
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