Activity of Liquid and Volatile Fractions of Essential Oils against Biofilm Formed by Selected Reference Strains on Polystyrene and Hydroxyapatite Surfaces

Abstract

Biofilms are surface-attached, structured microbial communities displaying higher tolerance to antimicrobial agents in comparison to planktonic cells. An estimated 80% of all infections are thought to be biofilm-related. The drying pipeline of new antibiotics efficient against biofilm-forming pathogens urges the search for alternative routes of treatment. Essential Oils (EOs), extracted from medicinally important plants, are a reservoir of bioactive compounds that may serve as a foothold in investigating novel antibiofilm compounds. The aim of this study was to compare antimicrobial activity of liquid and volatile fractions of tested EOs against biofilm-forming pathogens using different techniques. In this research, we tested five EOs, extracted from Syzygium aromaticum L., Boswelia serrata Roxb., Juniperus virginiana L., Pelargonium graveolens L. and Melaleuca alternifolia Cheel., against planktonic and biofilm forms of five selected reference strains, namely Staphylococcus aureus, Enterococcus faecalis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. To obtain cohesive results, we applied four various methodological approaches: to assess the activity of the liquid fraction of EOs, disc diffusion and the microdilution method were applied; to test EOs’ volatile fraction, the AntiBioVol assay and modified Antibiofilm Dressing Activity Measurement (A.D.A.M.) were used. The molecular composition and dynamics of antimicrobial substances released from specific EOs was measured using Gas Chromatography–Mass Spectrometry (GC-MS). The antimicrobial potency of EO’s volatile fraction against biofilm formed by tested strains differed from that of the liquid fraction and was related to the molecular weight of volatile compounds. The liquid fraction of CW-EO and volatile fraction of F-EO acted in the strongest manner against biofilm of C. albicans. The addition of 0.5% Tween 20 to liquid phase, enhanced activity of G-EO against E. coli and K. pneumoniae biofilm. EO activity depended on the microbial species it was applied against and the chosen assessment methodology. While all tested EOs have shown a certain level of antimicrobial and antibiofilm effect, our results indicate that the choice of EO to be applied against a specific biofilm-forming pathogen requires careful consideration with regard to the above-listed aspects. Nevertheless, the results presented in this research contribute to the growing body of evidence indicating the beneficial effects of EOs, which may be applied to fight biofilm-forming pathogens.

The Antimicrobial and Antibiofilm In Vitro Activity of Liquid and Vapour Phases of Selected Essential Oils against Staphylococcus aureus

“…In our study, liquid fractions of TT-EO emulsions exerted antibiofilm effect in concentration ranges from 6.3 to 0.8% ( v/v ) ( Table 3 ). These results are consistent with results of our previous studies in which we observed that liquid fractions of the EOs are able to reduce viability of staphylococcal biofilm cells in microdilution assays [ 50 , 53 ]. Feng et al have indicated complete removal of mature MRSA biofilm after the exposure to 0.32% TT-EO [ 62 ].…”

“…Tween 20 was used as non- ionic surfactant to enhance solubilization and reduce evaporation of EOs [ 52 ]. According to our previous research, addition of 0.5% ( v/v ) Tween 20 improved anti-staphylococcal activity of TT-EO liquid fractions [ 53 ]. As it is presented in Figure S1 in Supplementary Materials , Tween 20 did not inhibit growth of S. aureus planktonic cells in the concentrations used for emulsion preparation.…”

Bioactivity of Essential Oils for Mitigation of Listeria monocytogenes Isolated from Fresh Retail Chicken Meat

“…EOs were diluted using Tween 20 (0.5%, v / v ) [ 45 ] at the following concentrations 0.5, 0.25, 0.15, and 0.1% ( v / v ) and filtered using sterilized nylon syringe filters (0.22 µm). The antimicrobial activity was assessed by a standard disc diffusion assay [ 46 ].…”

Modifications of bacterial cellulose in wound care

“…Recently, the antimicrobial action of essential oils (EOs) has been of interest to some researchers. 27 Dudek-Wicher et al studied the antibiofilm efficacy of 3 essential oils: tea tree, geranium and frankincense essential oils, incorporated in BC against Gram-positive (S. aureus spp., Enterococcus faecalis spp.) and Gram-negative (Klebsiella pneumoniae spp., P. aeruginosa spp., E. coli spp.)…”

“…All tested EOs exhibited antibiofilm efficacy against the tested strains, with efficacy of nearly 80-100%, exhibited by tea tree and geranium essential oils. 27 Unlike antiseptics or antibiotics, the volatile property of EOs allows them to reach the areas neighboring the areas of application. Bacterial cellulose enriched with thymol, a component of an essential oil, was successfully applied on a third-degree burn wound closure.…”