Synergistic effects of three Moroccan thyme essential oils with antibiotic cefixime

The association of essential oils (EOs) with antibiotics provides a promising solution towards combating resistant bacteria. Thus, the aim of this study was to examine for the first time the possible synergistic interaction between EOs of three Moroccan thymes, namely Thymus leptobotrys (carvacrol [79.1%]), Thymus pallidus (γ-terpinene [29.6%], thymol [26.8%] and p-cymene [18.9%]) and Thymus ciliatus (carvacrol [26.2%], p-cymene [19.6%], thymol [17.3%] and γ-terpinene [14.6%]) and the antibiotic cefixime against selected pathogenic bacteria. The results showed that all thyme EOs presented interesting antibacterial potency and important synergistic effects with cefixime. Thymus leptobotrys EO showed the strongest efficacy against all tested bacteria (minimum inhibitory concentration values 0.14 mg/mL to 73.92 mg/mL), and the best synergistic effect (fractional inhibitor concentration indices: 0.26 to 0.5; gain: 4- to 130-fold). This synergistic interaction between the studied thyme EOs and cefixime may provide a basis for future applications for the control of antibiotic-resistant bacteria.