Evaluation of the antibacterial and anti-biofilm activities of essential oils against bovine mastitis causing pathogens

Bovine mastitis, the inflammation of the mammary gland, is a major concern for the dairy cattle community worldwide. The main mastitis-causing organisms are bacteria, classified as contagious, such as Staphylococcus aureus, Streptococcus dysgalactiae, and Streptococcus agalactiae ; and environmental, mainly Streptococcus spp . (e.g. S. uberis ) and coliforms species [ 1 ]. Although the development of antibiotic-resistant strains of pathogens has become a critical challenge, the primary treatment of mastitis is still using antibiotics [ 2 ]. Thus, looking for alternative therapies, such as essential oils (EO), is necessary [ 3 ] [ 4 ]. The present in vitro study aimed to assess the potential of essential oils as an alternative or complementary treatment to conventional antibiotics against pathogens that cause bovine mastitis. The bactericidal activity of 11 essential oils and 2 blends was investigated against 5 strains responsible for bovine mastitis: S. agalactiae, S. dysgalactiae, S. uberis, S. aureus, and S. epidermidis . The assessment of both the reduction of biofilm formation and the inhibition of pre-formed biofilm was carried out against biofilm-formative strains of S. aureus and S. epidermitis . Origanum vulgare and Cinnamomum zeylanicum resulted to be the most active essential oils against the above-mentioned bacteria, inhibiting both bacterial growth and biofilm formation. This research highlights the importance of evaluating natural products to strengthen the hypothesis of safe EO applications for reducing bacterial infections as effective antibiotic alternatives in complementary therapy. Furthermore, combinations of the available antibiotics and natural compounds should also be taken into consideration to avoid treatment failure. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany