Antimicrobial activity of oregano essential oil (Lippia graveolens K.) from Saucillo, Chihuahua against pathogens isolated from bovine mastitis

Abstract

Objective: To evaluate the antimicrobial activity of oregano (Lippia graveolens Kunth) essential oil sourced from Saucillo, Chihuahua, against bacterial pathogens isolated from clinical cases of bovine mastitis.

Design/Methodology/Approach: Milk samples were collected from cows exhibiting clinical signs of mastitis and subjected to bacterial isolation and identification using standard microbiological techniques. Antibiotic susceptibility profiles were determined, and the antimicrobial activity of the essential oil was evaluated through the disk diffusion method at four concentrations: 25%, 50%, 75%, and 100%.

Results: The most frequently isolated bacterial species were Staphylococcus aureus and Klebsiella pneumoniae. The oregano essential oil demonstrated significant inhibitory activity against both species, with inhibition zones increasing proportionally to concentration, reaching maximum values at 75% and 100%. Negative controls (distilled water and DMSO) showed no inhibitory effect, confirming the efficacy of the essential oil.

Limitations/Implications: Antibiotic susceptibility testing revealed that although most bacterial isolates were susceptible to conventional antibiotics, S. aureus exhibited resistance to penicillin and ampicillin, underscoring the need for natural alternatives. Findings/Conclusions: These results confirm the potential of Lippia graveolens essential oil as a natural or complementary antimicrobial agent for the control of bovine mastitis. Its application may contribute to reducing antibiotic overuse and support the adoption of more sustainable practices in dairy production.