Antibacterial and Synergistic Effects of Shirazi Thyme (Zataria multiflora) Essential Oil Against Methicillin-Resistant Staphylococcus aureus

Background Methicillin-resistant Staphylococcus aureus (MRSA) is a significant public health concern due to its resistance to multiple antibiotics, primarily mediated by the mecA gene, which encodes penicillin-binding protein 2a (PBP2a), given the urgent need for alternative antimicrobial agents. Materials and Methods A clinical MRSA strain harboring the mecA gene was identified. Antimicrobial susceptibility testing was performed to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Shirazi thyme ( Zataria multiflora ) essential oil. The strain’s susceptibility to multiple antibiotics was assessed and the synergistic effect of Zataria multiflora essential oil and cefoxitin was also evaluated. Gas chromatography-mass spectrometry (GC-MS) was employed to identify the bioactive compounds in the essential oil. Molecular docking studies were performed to evaluate the competitive binding affinity of those compounds to PBP2x. Results The MRSA strain exhibited resistance to all tested antibiotics except linezolid. The MIC and MBC values for Zataria multiflora essential oil were 3.125 mg.mL ^− 1 and 6.25 mg.mL ^− 1 for the reference S. aureus strain (ATCC 25923), and 6.25 mg.mL ^− 1 for both MIC and MBC for the clinical MRSA strain. The synergy assay demonstrated an enhanced inhibition zone for cefoxitin in combination with Zataria multiflora essential oil, indicating a synergistic interaction. Molecular docking studies revealed strong binding interactions between spathulenol, isospathulenol, and aromadendrene comparable to clinically used β-lactam antibiotics. Conclusion The findings highlight the significant antibacterial activity of Zataria multiflora essential oil against MRSA and its potential to enhance the efficacy of cefoxitin through synergistic interactions as natural inhibitors of PBP2x.