Mitigating Bovine Mastitis and Raw Milk Pathogen Risks: Inhibition of Staphylococcus xylosus by Mediterranean Plants'...

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.