Leveraging the antibacterial and antibiofilm activities of Cymbopogon flexuosus essential oil against multidrug-resistant bacteria recovered from avian colibacillosis and bovine mastitis: in vitro and molecular docking insights.

This study investigated the chemical composition and antibacterial and antibiofilm activities of Cymbopogon flexuosus essential oil (CFEO) against multidrug-resistant (MDR) bacteria within a One Health framework. The bacterial panel comprised four clinical isolates (n = 1 per source): a methicillin-resistant Mammaliicoccus sciuri (MR-M. sciuri) from bovine mastitis, a colistin-resistant ESBL-producing Escherichia coli (E. coli) from avian colibacillosis, and MR-Staphylococcus haemolyticus (MR-S. haemolyticus) and MDR Staphylococcus aureus (MDR S. aureus) from healthy farm personnel in contact with diseased animals. GC-MS analysis was performed to study the chemical composition of the CFEO. Antibacterial activities were evaluated via disk diffusion and broth microdilution assays. Disk diffusion was used exclusively as a qualitative screening tool to identify potential interactions; synergy was assessed definitively through the checkerboard assay by calculating the Fractional Inhibitory Concentration Index (FICI). The antibiofilm activity of CFEO was quantified via Congo red agar, crystal violet staining, and light microscopy. Molecular docking simulation was performed to assess the binding interactions of the CFEO constituents with key bacterial proteins. The major constituents of CFEO were geranial (α-citral; 32.98%), neral (β-citral; 28.62%), β-terpinene (11.50%), geraniol (5.42%), nerol acetate (3.40%), and linalool (2.31%). The inhibition zones ranged from 38 ± 2.00 to 56 ± 1.00 mm, while the MIC values spanned from 8 to 8192 µg/mL. CFEO demonstrated a synergistic effect with oxacillin against MR-M. sciuri (FICI = 0.28). Sub-MIC concentrations of CFEO significantly disrupted the biofilms of M. sciuri and E. coli. Bioinformatics analysis via molecular docking revealed favorable binding affinities between major compounds of CFEO and key bacterial proteins, including PBP2a, SarA, and AgrA. This study highlights the in vitro efficacy of CFEO against MDR, MR and biofilm-forming bacteria circulating at the animal-human interface, as well as its synergistic potential when combined with oxacillin against MR-M. sciuri. Molecular docking analyses suggest that the major compounds of CFEO may act as promising adjuvants in the development of new therapeutic strategies against MDR bacteria within a One Health framework.