Antibacterial activity of rheum rhaponticum, olea europea, and viola odorata on ESBL-producing clinical isolates of escherichia coli and klebsiella pneumoniae

Abstract

The aim of this study was to determine the antimicrobial activity of three selected Lebanese plants (Rheum rhaponticum, Olea europaea, and Viola Odorata) against Extended Spectrum Beta Lactamase (ESBL) – producing Escherichia coli and Klebsiella pneumoniae, and to identify the specific plant fraction responsible for the antimicrobial activity. The plants were extracted with ethanol to yield the crude extract which was further subfractionated by different solvents to obtain the petroleum ether, the dichloromethane, the ethyl acetate and the aqueous fractions. The Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) were determined using broth microdilution. The MICs ranged between 2.5 and 80 μg/μl. The majority of these microorganisms were inhibited by 80 and 40 μg/μl of the crude extracts. The dichloromethane fraction of Olea europea exerted a significant inhibitory effect on 90% of the tested strains. Ethyl acetate extracts of all selected plants presented antibacterial activity with high potency. Aqueous extracts of Rheum rhaponticum and Olea europaea exerted antimicrobial activity against the majority of the tested strains while Viola Odoratas aqueous extract showed less activity. This study constitutes a good example for the screening of antimicrobial activities of plants on highly resistant organisms of clinical importance; however, toxicity of these extracts needs more investigation.