# Evaluation of a Commercial Ozonated Olive Oil Product (800 mEq O2/Kg) Against Methicillin-Resistant Staphylococcus pseudintermedius (MRSP) Using an Ex Vivo Canine Skin Model

## TL;DR

A commercial ozonated olive oil showed antibacterial effects in lab tests but failed to reduce MRSP bacteria in a canine skin model, highlighting the need for real-tissue testing.

## Contribution

Demonstrated that in vitro antibacterial activity of ozonated olive oil does not translate to ex vivo skin efficacy against MRSP.

## Key findings

- Ozonated olive oil exhibited bactericidal effects in vitro with MIC < 20% v/v.
- Ex vivo canine skin showed no MRSP reduction after 8 hours of treatment with ozonated or placebo oil.
- Bacterial localization in the superficial dermis remained unchanged in ex vivo tests.

## Abstract

Background: Methicillin-resistant Staphylococcus pseudintermedius (MRSP) represents an emerging challenge in veterinary dermatology. Commercially available ozonated oils promise antibacterial activity, but their efficacy under physiologically relevant conditions remains unexplored. Objective: We aimed to evaluate the efficacy of commercial ozonated olive oil product (800 mEq O2/kg) against MRSP using an established in vitro model and a newly presented ex vivo canine skin model. Materials and Methods: In vitro susceptibility testing determined minimum inhibitory concentrations (MIC) and time–kill kinetics. Subsequently, canine skin samples were mounted in Franz diffusion cells, inoculated with MRSP (~106 colony-forming units [CFU]), and treated for 8 h with ozonated or placebo olive oil. Bacterial viability was assessed by quantitative culture and histopathology. Results: In vitro testing demonstrated antibacterial activity for ozonated oil (MIC < 20% v/v) compared to placebo oil (90% v/v), with ozonation-specific bactericidal effects. However, ex vivo testing showed no MRSP reduction for either oil versus untreated controls, with bacterial localization in superficial dermis unchanged. Conclusions: Despite in vitro activity, this ozonated olive oil failed to reduce MRSP in ex vivo skin, revealing that tissue barriers prevent antibacterial delivery. These findings demonstrate that in vitro screening cannot predict topical efficacy and emphasize the necessity of tissue-based validation before clinical use.