Comparative Evaluation of Synergistic Antibacterial Effects in Blended Essential Oil against Gram-Positive and Gram-Negative Pathogens

Abstract

The rising emergence of multidrug-resistant bacteria has heightened the search for novel antibiotic agents. Essential Oils (EOs) are complex combinations of volatile organic compounds generated by plants, with many exhibiting significant antimicrobial properties. This study evaluates the antibacterial movement of single and blended EOs against representative gram-positive bacteria Staphylococcus aureus and Methicillin-Resistant S. aureus (MRSA) and gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Using the disk diffusion method, blended EOs exhibited greater inhibition zones than those of singles, with gram-positive bacteria (S. aureus and MRSA) being more susceptible than gram-negative bacteria. Notably, P. aeruginosa demonstrated complete resistance, likely due to its complex outer membrane. The Minimum Inhibitory Concentration (MIC) was decided via micro-well dilution assay in line with the Clinical and Laboratory Standards Institute criteria, further validating the enhanced efficacy of blended EOs. Synergistic interactions among active components in the EOs likely contributed to the lower MIC values observed for blended EOs. This study highlights the blended EOs as essential antibacterial agents, particularly against gram-positive pathogens such as MRSA. However, resistance in gram-negative bacteria highlights the need for targeted formulation strategies. Future research should focus on evaluating EO efficacy against diverse multi-drug resistance pathogens, optimizing EO formulations for clinical practice. These results support the development of EO-based therapies as sustainable alternatives to synthetic antimicrobials in combating multi-drug resistant infections. The study establishes the framework for incorporating EOs into antimicrobial strategies, addressing the crucial need for novel solutions to the global antibiotic resistance challenge.