Introduction. The opportunistic pathogen Pseudomonas aeruginosa, like all members of the genus Pseudomonas, has the capacity to thrive in very different environments, such as water, plant roots, animals, including humans in whom it can cause severe infections especially in immunocompromised patients. Infections by P.aeruginosa are notoriously difficult to treat due to its intrinsic ability to resist many classes of antibiotics as well as its ability to acquire resistance. Given the severity of P.aeruginosa infections and the limited antimicrobial arsenal with which to treat them, finding alternative prevention and treatment strategies is an urgent priority. Hence, the objective of our study was to investigate the in vitro antibacterial activity of some essential oils (EOs) and their main components against P.aeruginosa strains. Amikacin (AMK) was used as reference drug. Materials and Methods. A clinical multidrug resistant P.aeruginosa (MDR-PA) strain and P.aeruginosa ATCC 27853 were used. The EOs of Mentha X piperita and Thymus vulgaris and their main components (menthol and thymol) were tested for in vitro antibacterial activity. The EOs and components were purchased from Erbe Aromatiche Essenzialmenta (Pancalieri, Italy) and Primavera/Flora (Pisa, Italy). AMK was commercially purchased (Sigma-Aldrich, Milano, Italy). The chemical composition of the EOs was analysed by Gas Chromatography–Mass Spectometry (GC/MS). The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of EOs, components and AMK were evaluated by means of the twofold serial microdilution assay according to the CLSI M100-S25 (2015) with some modifications for EOs. The final concentrations ranged from 4% to 0.0078% (v/v). Results. In this study, the results showed that all tested oils were ineffective on MDR-PA and P.aeruginosa ATCC 27853 strains. In fact, the MIC and MBC values ranged from 4% to >4% (v/v). Conversely, the menthol and thymol displayed an interesting activity: the MIC value of menthol was 0.25% v/v against MDR-PA (MBC=0.25% v/v) and P.aeruginosa ATCC 27853 (MBC=>2% v/v). The MIC value of thymol was 0.125% v/v against MDR-PA (MBC=0.25% v/v) and P.aeruginosa ATCC 27853 (MBC=0.5% v/v). Discussion and Conclusions. Several studies have reported that P. aeruginosa appear to be least sensitive to the action of EOs. In the present study, the main components demonstrated promising antimicrobial activities against this bacterium. These results provide significant information on the activity of these components, suggesting their potential use. These encouraging results require further confirmation, to better clarify these data.
Comparative evaluation of the inhibitory effect of some essential oils against Multidrug Resistant Pseudomonas aeruginosa
MANDRAS Narcisa;SCALAS Daniela;ROANA Janira;BANCHE Giuliana;ALLIZOND Valeria;CUFFINI Annamaria;TULLIO Vivian
2018-01-01
Abstract
Introduction. The opportunistic pathogen Pseudomonas aeruginosa, like all members of the genus Pseudomonas, has the capacity to thrive in very different environments, such as water, plant roots, animals, including humans in whom it can cause severe infections especially in immunocompromised patients. Infections by P.aeruginosa are notoriously difficult to treat due to its intrinsic ability to resist many classes of antibiotics as well as its ability to acquire resistance. Given the severity of P.aeruginosa infections and the limited antimicrobial arsenal with which to treat them, finding alternative prevention and treatment strategies is an urgent priority. Hence, the objective of our study was to investigate the in vitro antibacterial activity of some essential oils (EOs) and their main components against P.aeruginosa strains. Amikacin (AMK) was used as reference drug. Materials and Methods. A clinical multidrug resistant P.aeruginosa (MDR-PA) strain and P.aeruginosa ATCC 27853 were used. The EOs of Mentha X piperita and Thymus vulgaris and their main components (menthol and thymol) were tested for in vitro antibacterial activity. The EOs and components were purchased from Erbe Aromatiche Essenzialmenta (Pancalieri, Italy) and Primavera/Flora (Pisa, Italy). AMK was commercially purchased (Sigma-Aldrich, Milano, Italy). The chemical composition of the EOs was analysed by Gas Chromatography–Mass Spectometry (GC/MS). The Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of EOs, components and AMK were evaluated by means of the twofold serial microdilution assay according to the CLSI M100-S25 (2015) with some modifications for EOs. The final concentrations ranged from 4% to 0.0078% (v/v). Results. In this study, the results showed that all tested oils were ineffective on MDR-PA and P.aeruginosa ATCC 27853 strains. In fact, the MIC and MBC values ranged from 4% to >4% (v/v). Conversely, the menthol and thymol displayed an interesting activity: the MIC value of menthol was 0.25% v/v against MDR-PA (MBC=0.25% v/v) and P.aeruginosa ATCC 27853 (MBC=>2% v/v). The MIC value of thymol was 0.125% v/v against MDR-PA (MBC=0.25% v/v) and P.aeruginosa ATCC 27853 (MBC=0.5% v/v). Discussion and Conclusions. Several studies have reported that P. aeruginosa appear to be least sensitive to the action of EOs. In the present study, the main components demonstrated promising antimicrobial activities against this bacterium. These results provide significant information on the activity of these components, suggesting their potential use. These encouraging results require further confirmation, to better clarify these data.
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