Introduction: Medicinal plants possess plentiful of bioactive molecules effective against multi-resistance bacteria. The aim of this study is to assess the in vitro antimicrobial activities of essential oils extracted from three Moroccan aromatic plants. Method:Analysis of essential oils of Origanum compactum, Rosmarinus officinalis and Pelargonium asperum, collected from different localities in Morocco was performed using a GC-MS spectrophotometry. Antibacterial activity by disc diffusion assay was evaluated in vitro against five clinical multi-resistant isolates.Results: Origanum showed strong antibacterial activity against tested strains except Pseudomonas aeruginosa while Rosmarinum showed a bactericidal effect against Acinetobacter baumanii, Escherichia coli and Staphylococcus aureus. Pelargonium presented only slight growth inhibition of Staphylococcus aureus on solid medium. Interestingly, fractions F7 and F8 of Pelargonium which represented only 0.3% and 0.1% respectively of the total mass were found to be bactericidal against Klebsiella pneumoniae and Pseudomonas aeruginosa. Conclusions:Ours results showed that the antimicrobial activities were variables depending on the chemical composition of essential oils, the fraction used and the microorganism tested.Essential oils fractionation allows detection of bioactive substances, especially those owning antimicrobial activity and present in small quantities. IntroductionThe overuse of antibiotics to treat infectious diseases resulted in the emergence of multidrug resistance (MDR) bacteria. Actually, this increased phenomenon is currently considered as a major threat to global public health. This has prompted the World Health Organization (WHO) to direct research into new alternatives and especially to plants that have always constituted a source of ongoing bioactive molecules and current inspiration for new medicines. Delacroix in 1881 showed for the first time the essential oils (Eos) action against bacteria [1]. Since then, numerous studies have been reported the in vitro antimicrobial activities of certain chemical compounds of various plant extracts [2]. The capacity of certain essential oils to neutralize germs is now irrefutable [3].Origanum compactum, Rosmarinus officinalis and Pelargonium asperum are wildly used plants over the world and particularly in Mediterranean countries. They are known for their aromatic, gastronomic and phytotherapeutic features. Hence, EO extracted from these plants is actively investigated for antimicrobial effect [4], as they could substitute antibiotics in the treatment of infectious diseases caused by multi-resistant bacteria (MRB).The mode of action of EOs on bacteria is not clearly elucidated, but for the variety of molecules in these oils, it seems that their effect results from a combination of several modes of action that involve various cell targets [5].This study was carried out aiming to perform qualitative and quantitative analyses and to assess the in vitro antimicrobial activities of EOs extracted fr...

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