Antimicrobial effect of ozone on E.faecalis in-vitro

Aim: To assess the ability of using ozone or air or sodium hypochlorite and air treatment to kill a strain of Enterococcus faecalis in an in-vitro pilot study. Methods: E. faecalis was cultured overnight on blood agar plates. A suspension of the microorganisms was made up to an approximate concentration of 108/ml using McFarland Standards in Phosphate Buffered Saline (PBS). Serial dilutions to 107, 106, 105 and 104/ml were made. 50 microlitre of each concentrate were pipetted into wells. The HealOzone (KaVo) device produced gaseous ozone at 2100 ppm or air at a flow rate of 102.5 cc/min. Ozone or air was bubbled at different exposure times of 10, 20, 40, 60 or 120s compared with NaOCl with air into suspensions of E. faecalis. Results: The use of gaseous ozone or sodium hypochlorite with air for 120 seconds killed all E. faecalis, when its concentration in suspension is 5.9 x 107 or less for ozone and 5.8 x 106 or less for NaOCl. Air had no significant effect. Sodium hypochlorite was less effective than ozone in reducing the number E. faecalis in the lower times of application; it takes more time to reduce the number of the microorganisms. The application of ozone gas for a period of 10 to 120 seconds was capable of reducing the number of E. faecalis more than NaOCl and air and total eradication of E. faecalis occurred after ozone treatment with an exposure time of 40 seconds or more when the starting bacterial concentration was 5.9 x 104 for 40s and 5.8 x 106 for 60 or 120s. Conclusion: Air had no effect compared to ozone gas or NaOCl and air. Ozone gas had a significant antimicrobial effect against E. faecalis compared to NaOCl which takes more time to achieve its effects.