In recent years, there has been a growing interest in researching and developing new antimicrobial agents from various sources to combat microbial resistance. Therefore, a greater attention has been paid to antimicrobial activity screening and evaluating methods. Several bioassays such as disk-diffusion, well diffusion and broth or agar dilution are well known and commonly used, but others such as flow cytofluorometric and bioluminescent methods are not widely used because they require specified equipment and further evaluation for reproducibility and standardization, even if they can provide rapid results of the antimicrobial agent's effects and a better understanding of their impact on the viability and cell damage inflicted to the tested microorganism. In this review article, an exhaustive list of in vitro antimicrobial susceptibility testing methods and detailed information on their advantages and limitations are reported.

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The combination of essential oils (EOs) is a novel alternative to improve their preservative effects and to reduce their organoleptic impact in food. In this context, this work aims to investigate the antibacterial combined effect of two EOs combinations through the calculation of the fractional inhibitory concentration index. The combinations tested consists of Lavandula dentata/Origanum majorana EOs and Thymus serpyllum/Origanum majorana EOs. Their chemical compositions were identified by CG/MS analyses. The main compounds of O. majorana EO were (-)-terpinene-4-ol and trans-4-thujanol. Those of L. dentata EO were β-pinene and 1,8-cineole, and those of T. serpyllum EO were p-cymene and γ-terpinene. Regarding the outcomes, results highlighted partial synergistic and additive interactions. Two combinations of marjoram and thyme EOs had antibacterial activities against S. aureus. The first one corresponded to the quarter of the minimum inhibitory concentration of marjoram and half that of thyme. The second one was the mix of half and quarter of the minimum inhibitory concentration of respectively marjoram and thyme EOs. This last combination also showed an antibacterial effect against E. coli. The quarter and the half of their minimum inhibitory concentration of marjoram and lavender combination, respectively, gave a partial synergy against both strains. Henceforth, these findings could be largely exploited in food preservation through the use of minimal doses of these plant products without affecting the antibacterial and the organoleptic properties in foods.

Novel drugs for methicillin-resistant Staphylococcus aureus (MRSA) hospital- and community-acquired infections are needed because of the emergence of resistance against antibiotics. In this study, methanolic and aqueous extracts of Berberis hispanica, Crataegus oxyacantha, Cistus salviifolius, Ephedra altissima, and Lavandula dentata selected from an ethnopharmacological study to treat skin infections in Sefrou city (Center of Morocco) were tested for their antistaphylococcal activity against strains often involved in cutaneous disorders: two methicillin-resistant Staphylococcus aureus strains and one strain of Staphylococcus epidermidis using the well-diffusion assay, while the agar macrodilution method was used to determine the minimal inhibitory concentrations. The total phenolic compounds and flavonoid contents of all tested extracts were also evaluated. Three of the five methanolic extracts showed an important antibacterial activity. Berberis hispanica extract was the most active with a minimal inhibitory concentration of 04.00 mg/ml against all tested strains, followed by Cistus salviifolius and Crataegus oxyacantha extracts containing the highest amounts of total phenols (133.83 ± 9.03 and 140.67 ± 3.17 μg equivalent of gallic acid/mg of extract). However, the aqueous extracts have not shown any activity against the tested strains. The current data suggested that the most active extracts can be a good source of natural antistaphylococcal compounds and warrants further investigations to isolate bioactive molecules.

In this work, the chemical composition, the antioxidant, and the antibacterial activities of two Moroccan essential oils less studied, extracted from Pelargonium asperum and Ormenis mixta, were investigated. According to the gas chromatography coupled to mass spectrometry analysis, citronellol (25.07%), citronellyl ester (10.52%), geraniol (10.46%), and buthyl anthranilate (5.93%) were found to be the major components of P. asperum, while O. mixta was mainly composed of D-germacrene (11.46%), 1,8-cineole (10.28%), and cis-methyl isoeugenol (9.04%). Moreover, O. mixta essential oil exhibited an important antioxidant activity being significantly higher than that exhibited by P. asperum oil (P < 0.001). As regards the antimicrobial activity of both essential oils, the zones of growth inhibition and the minimum inhibitory concentration values showed that P. asperum essential oil was more active than that of O. mixta. Thereafter, the impact of the binary combination of essential oils on their antimicrobial effect was investigated against Staphylococcus aureus using the fractional inhibitory concentration index calculation. The results showed a promising synergistic antibacterial interaction between essential oils studied.

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In order to increase the Moroccan Pistacia lentiscus L. value, the antibacterial activity of its twig's and leave's essential oils was evaluated. The study of antibacterial activity was performed on Gram positive bacteria Bacillus subtilis, Staphylococcus aureus and Gram-negative bacteria Escherichia coli, Pseudomonas aeruginosa by the microdilution method. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of leaves and twigs essential oils against the four studied strains were determined and showed that both essential oils tested have remarkable antibacterial activity. Bacillus subtilis was the most sensitive strain against the two essential oils while Pseudomonas aeruginosa was the most resistant one.

Objective: As part of the valorization of medicinal and aromatic plants in Morocco, this study aims to investigate the chemical composition, the antimicrobial and the antioxidant activities of Mentha pulegium essential oil.Methods: Essential oil of M. pulegium from Oued Laou region (Morocco) was screened for its antimicrobial activity against seven bacteria and two fungi using broth microdilution method. The radical scavenging effect was used to assess in vitro antioxidant capacity of this oil. Results:The tested essential oil exhibited strong inhibitory effect against all tested microorganisms with minimum inhibitory concentrations ranging from 0.003% to 1% (v/v) except for Pseudomonas aeruginosa. Moreover, the studied essential oil exhibited radical scavenging power with the half maximal inhibitory concentration of 2 mg/ml. Conclusion:These findings showed that the studied essential oil has both an antimicrobial and antioxidant potential, which is very rare. Thus, it reinforces its use as an effective, eco-friendly preservative agent in food and cosmetic field.