Exploring synergistic effects of Piper betle and Anethum graveolens essential oils with antibiotics against Methicillin-resistant Staphylococcus aureus: Insights from In silico targeting of PBP2a

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of infections worldwide, and remains challenging due to its resistance mechanisms. This study investigated potential synergistic antimicrobial activity of essential oils from Piper betle (PBEO) and Anethum graveolens (AGEO) in combination with conventional antibiotics against MRSA. Molecular docking simulations (MDS) were performed to explore the interactions with key components of essential oils and target protein Penicillin-Binding Protein 2a (PBP2a), which contributes to antibiotic resistance. Synergistic antibacterial effects were evaluated using clinical MRSA isolates and a reference strain, through broth microdilution, checkerboard, and time-kill assays. Amongst all the combinations tested, antibiotic tetracycline exhibited synergistic (FICI <0.5) and additive (FICI >0.5 < 1) interactions for both essential oils. Time-kill confirmed essential oil-antibiotics enhanced anti-MRSA activity when compared to their individual effects over 24 h. MDS showed strong interactions with major components of PBEO and the allosteric site of PBP2a, when compared to the components of AGEO. In silico findings from the study showed molecular interactions underlying the antimicrobial effects, supporting experimental data and highlighting PBEO and AGEO with tetracycline as promising anti-MRSA therapeutic candidates.