Inactivation of some bacterial species for surfaces disinfection by ozone

Ozone (O3) is an unstable gas used commonly for oxidation and disinfection. It is approximately 20 times more soluble than oxygen in water. Ozone is a protoplasmic oxidant affecting the bacterial proteins and inactivates cellular enzymes. It can destroy molds, bacteria and viruses. The present study was conducted to assess the disinfecting ability of ozone on the surface microorganisms. Eight species of pathogenic bacteria in different concentrations (102, 105, 107 and over than 107 cells per milli liter) were treated with ozone gas. An aluminum chamber with a total capacity of 300L was set within a safety cabinet, where the ozone generator was installed. Different concentrations of 8 species of bacteria were treated with ozone gas at different times (30, 60, 90, 120, 180 minutes). Before and after ozone treatment, the number of bacteria was determined by breed counter method. Among different bacteria treated with ozone, Bacillus cereus revealed the highest resistance to the germicidal effects of ozone. Indeed, concentration of >107 cells/ml of this microorganism was inactivated by the highest ozone concentration (30 ppm). Staphylococcus aureus and Micrococcus spp. with concentration of 107 cells/ml were inactivated with lower ozone concentration (10 ppm), however, Escherichia coli and other gram-negative bacterial pathogens (107 cells/ml) were inactivated in higher concentration of (15 ppm) ozonation. In order to achieve surface sterilization, ozone should be employed with a concentration of 30 ppm, however, if inactivation of nonsporulative bacteria is desired lower ozone concentration of 15 ppm will be adequate.