The In Vitro Effect of Ozone Therapy Against Equine Pythium insidiosum

The goal of the present study was to characterize the antimicrobial action of different ozone (O₃) presentations against Pythium insidiosum isolated from horses. In experiment 1, P. insidiosum was treated with ozonated distilled water, ozonated sunflower oils with distinct peroxide indexes or O₃ gas (72 μg O₃ mL^-1). In experiment 2, samples were exposed one or three times to oxygen (O₂) or O₃ gas (72 μg O₃ mL^-1; 30 min/day). In experiment 3, P. insidiosum was treated with different concentrations of O₃ gas (Ø, 32, 52, or 72 μg O₃ mL^-1) for three days (30 min/day). In experiment 4, samples were exposed to O₂ or O₃ gas (72 μg O₃ mL^-1) for 05, 15, or 30 minutes during three days. Posteriorly, all samples were cultured for two weeks, and the pathogen growth area was measured until D14. Samples with absence of growth on D14 were recultured to assess the germicidal or germistatic action of the treatment. In experiment 1, only ozonized sunflower oil with a high peroxide index had germicidal action against the pathogen. In experiment 2, samples exposed three times to O₃ gas were inactivated. In experiment 3, the O₃ therapy had germicidal action against P. insidiosum independently of the gas concentration (P > .1). In experiment 4, O₃ treatments ≥15 minutes suppressed the pathogen development, whereas samples exposed to O₃ gas for 5 minutes had progressive growth (P < .01). In conclusion, ozonated sunflower oil with a high peroxide index and multiple exposures to O₃ gas mixtures were able to inactivate P. insidiosum isolated from horses.