Synergistic antibacterial and antibiofilm potential of essential oils from Origanum compactum cultivated in an arid Mediterranean environment

This study investigated the chemical composition, antimicrobial and antibiofilm potential of essential oils (EOs) extracted from cultivated Origanum compactum (Benth.) from two provenances (Chaouen and Toufliht) under arid Mediterranean conditions over two years. EOs, obtained by hydrodistillation, were analyzed by GC-MS. Antibacterial activity was tested against six bacterial strains using diffusion and microdilution assays, while synergistic effects with ampicillin, kanamycin, and streptomycin were assessed by the checkerboard method. Biofilm inhibition and eradication were evaluated by the crystal violet assay. Chemical profiles were dominated by carvacrol (34.3-81.48%), p-cymene (3.44-24.21%), and γ-terpinene (0.02-29%). All EOs exhibited strong antibacterial activity, with Toufliht oils showing the lowest MICs (0.020-0.313 mg/mL). Synergistic and additive interactions (FICI ≤ 1) were observed, particularly against Gram-positive bacteria. Notably, Toufliht EO, with the highest carvacrol content, achieved strong biofilm inhibition (84.95%) and eradication (79.21%), representing a promising natural alternative to counter microbial resistance.