Binary Synergistic Combinations of Lavender and Fennel Essential Oils with Amoxicillin.

Microbial resistance is an important problem in modern healthcare systems. In addition to drug resistance, the side effects of current antibiotic applications are also known issues. In this present study, binary combinations of amoxicillin with European Pharmacopoeia quality lavender () and fennel () essential oils were evaluated against human pathogenic microbial strains. The checkerboard method was used to quantify the efficacy of the essential oils in combination with amoxicillin. As an initial result, remarkable antimicrobial activity was observed at relatively low amoxicillin concentrations using different oil combinations against ATCC 6538, ATCC 29212, ATCC 14579, NRRL B-3008, (clinical isolate), respectively. Fractional inhibitory concentrations were calculated and interpreted in terms of addition, synergy, antagonism, or indifferent. A synergistic interaction with the combination essential oil and amoxicillin (fractional inhibitory concentration index = 8.05 × 10) was observed against the pathogens and . Both essential oils together and in combination with amoxicillin showed a synergistic effect with possible future applications.