Antibacterial and Anti-biofilm Efficiency of Twenty Algerian Plants Essential Oils Against Resistant Acinetobacter baumannii

Abstract

The present study evaluated the antibacterial activity of twenty essential oils from Algerian plants against the multi-drug resistant (MDR), the extended-drug resistant (XDR), the pan-drug resistant (PDR) and the wild strains of Acinetobacter baumannii: a major human pathogen for which only a few effective treatments are nowadays available. Special attention was also given to their effect on A. baumannii biofilm formation. The chemical composition of the essential oils was determined by gas chromatography and gas chromatography-mass spectrometry analysis, while the antibacterial activity was determined by disc diffusion and microdilution broth sensitivity assays. Microscopic visualization highlighted the effect of the most active essential oils on biofilm formation. Molecular docking was performed to investigate the binding mode of imipenem, thymol and cinnamaldehyde against target proteins (PBP1, OMPA and IMP2). Eight of the twenty essential oils showed very good activities against resistant A.baumannii with inhibition zones greater than 20 mm. Ammoides verticillata essential oil recorded the lowest minimum inhibitory concentrations, biofilm inhibition and biofilm eradication concentrations values no more than 0.217 mg/mL, 0.48 mg/mL, and 0.48 mg/mL, respectively. A. verticillata and C. cassia not only inhibited biofilm formation but also weakened and dissolved pre-formed biofilms. The in-silico and in-vitro studies showed that phytochemical analogues, thymol and cinnamaldehyde had improved physicochemical characteristics, greater binding affinities and, a better anti-Acinetobacter activity comapared to imipenem. The results of this study suggest that essential oils and their individual components can be used as therapeutic substances and as cleaning products since they are effective and eco-friendly.