In Vitro Inhibitory Effect of Four Essential Oils against Fluoroquinolone- Resistant Enterobacteriaceae Responsible for Community-Acquired Urinary Tract Infections

The emergence of antibiotic resistance genes has highlighted the need to discover new drugs for the treatment of infections caused by multidrug-resistant bacteria. The study aims to investigate the antibacterial and anti-adhesive effect of four essential oils (EOs) from aromatic medicinal plants: Ammoides verticillata, Origanum glandulosum, Thymus fontanesii, and Thymus capitatus, against fluoroquinolones-resistant uropathogenic Enterobacteriaceae. The chemical composition of the oils was determined by gas chromatography-mass spectrometry GC/MS, the antibacterial activity was assessed using disc diffusion and micro-dilution methods, while the adhesion assay was carried out using light microscopy. The essential oils of Thymus fontanesii and Thymus capitatus were carvacrol chemotype, whereas Ammoides verticillata and Origanum glandulosum EOs were thymol chemotype. Sixteen Enterobacteriaceae with different fluoroquinolones-resistance profiles were isolated, belonging to Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis species. The inhibition zone diameters ranged from 17.67 ± 0.58 to 31 ± 0.00 (mm), Thymus capitatus EO appears to be the most effective, with the minimum inhibitory concentrations ranging from 0.5 mg/mL to 7.5 mg/mL. The lowest MIC (0.5 mg/mL) was observed for Thymus capitatus EO against Escherichia coli resistant strains. The adhesion assay showed a good adhesion reduction of the test Escherichia coli for all EOs, varying from 79% to 90%. These findings indicate that the studied essential oils can be used as a promising drug in the prevention and treatment of infections caused by resistant Enterobacteriaceae, however, exploring their therapeutic use requires thorough investigations that involves rigorous clinical studies to ensure their safety and efficacy.