# Mitigating Bovine Mastitis and Raw Milk Pathogen Risks: Inhibition of Staphylococcus xylosus by Mediterranean Plants’ Essential Oil

## TL;DR

This study shows that essential oils from Mediterranean plants can inhibit the growth of Staphylococcus xylosus in raw milk, offering a natural way to improve dairy safety.

## Contribution

The study introduces a natural, plant-based approach using essential oils to control Staphylococcus xylosus in raw milk.

## Key findings

- The essential oil blend from myrtle and sage showed strong antibacterial activity against Staphylococcus xylosus.
- Minimum Inhibitory Concentration analysis revealed effective inhibition at low concentrations (0.5–0.25%).
- The oils could serve as a natural alternative to antibiotics in food safety practices.

## Abstract

Milk can contain bacteria that are harmful to humans, especially when it comes from cows with early signs of udder infections that do not yet show symptoms. Some of these bacteria, like Staphylococcus xylosus, may be involved in the cheese-making process but can also pose risks to food safety. In this study, we found Staphylococcus xylosus in raw cow milk and tested whether certain plant-based essential oils could help control its growth. These oils came from three Mediterranean plants: myrtle, sage, and rockrose. We discovered that the oil blend had the ability to stop the bacteria from growing, especially when myrtle and sage were used. These results suggest that combining these essential oils could be a natural and effective way to improve the safety of milk and dairy products. This approach may also help reduce the use of traditional antibiotics, which is important in the fight against antimicrobial resistance. The findings could support safer food production and healthier outcomes for both animals and people.

Milk is frequently susceptible to contamination by potential pathogens, posing risks to both food safety and public health. Cheesemaking often relies on raw milk, where microbial communities—including Staphylococcus xylosus—can play a dual role: (i) contributing to fermentation and (ii) acting as opportunistic pathogens that can be often present in subclinical mastitis and be subjected to carry over in dairy products. In this study, Staphylococcus xylosus was isolated from raw bovine milk (preclinical mastitis) and identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (Biotyper scores: 1.87–2.19). Its susceptibility to erythromycin and to an essential oil blend composed of Myrtus communis, Salvia officinalis, and Cistus ladanifer was evaluated. The essential oil blend produced inhibition zones ranging from 9 mm to 13.3 mm, indicating moderate antibacterial activity. Further Minimum Inhibitory Concentration analysis revealed that Myrtus communis, Salvia officinalis, and the essential oil blend inhibited Staphylococcus xylosus growth at concentrations between 0.5 and 0.25 percent, while Cistus ladanifer required higher levels (1 to 0.5 percent). These findings suggest that selected essential oils—especially in combination—hold promise as complementary antimicrobial agents in food safety and antimicrobial resistance mitigation efforts.