Chemical profiling and anti-biofilm efficacy of Hyssopus officinalis L. essential oil against bovine mastitis pathogens: A promising natural alternative

The increasing prevalence of antibiotic-resistant pathogens and the economic burden of bovine mastitis necessitate the exploration of natural therapeutic alternatives. This study investigated the chemical composition, antimicrobial and anti-biofilm activities of Hyssopus officinalis L. (hyssop) essential oil (EO) against major bovine mastitis pathogens: Salmonella enterica, Escherichia coli, Staphylococcus aureus and Enterococcus faecalis. Gas chromatography–mass spectrometry (GC-MS) analysis identified 37 compounds, with bicycloheptane (20.75 %), 1,5,8-o-menthatriene (4.48 %), cyclohexanemethanol (3.79 %), spathulenol (3.70 %) and myrtenol (3.25 %) as the predominant constituents. Antimicrobial evaluation revealed that E. faecalis was the most susceptible bacterium (minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) = 0.0312 mg/mL), while S. enterica exhibited the highest resistance (MIC/MBC ≥5 mg/mL). The EO demonstrated strong anti-biofilm activity, with the most pronounced effect against E. faecalis (up to 81 % inhibition at 60 mg/mL) and the least against S. enterica (57 % inhibition at the same concentration). This study provides the first comprehensive evidence linking the specific chemical profile of hyssop EO to its potent anti-biofilm and antimicrobial action against bovine mastitis pathogens, suggesting its potential as a viable natural alternative to conventional antibiotic therapies.