DETERMINATION OF ANTIMICROBIAL ACTIVITY OF COMMERCIALLY AVAILABLE THYME ESSENTIAL OIL SAMPLES

Abstract

In this study, the antimicrobial efficacy of four commercial brands of thyme essential oil, sourced from four different vendors (pharmacy, e-commerce, herbalist, and supplier), was evaluated and compared according to their place of purchase. The research utilized standard strains, including Gram-negative bacteria Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853; Gram-positive bacteria Staphylococcus aureus ATCC 29213 and Bacillus cereus ATCC 14579; and fungi Candida albicans ATCC 10231 and Candida tropicalis DSM 11953. Antimicrobial activity was determined using the Minimum Inhibitory Concentration (MIC) method. Among the four brands tested at ten different concentrations on four bacterial and two fungal strains, the thyme essential oil sourced from the pharmacy demonstrated the highest level of antimicrobial activity. Based on our experimental results, the essential oils demonstrated the strongest inhibitory activity against Candida albicans, whereas Staphylococcus aureus exhibited the highest resistance to the tested oils.. All tested concentrations of essential oil samples allowed the growth of S. aureus. These findings indicate that essential oils sold in the market and online, intended for therapeutic purposes, vary significantly in quality. Economic incentives may lead to adulteration of these oils, underscoring the importance of using plant material from the correct species and considering the geographical conditions that influence the plant’s chemical composition. The superior antimicrobial efficacy of the pharmacy-sourced thyme essential oil highlights the need to rely on trained health professionals when selecting products for health-related purposes.