Anti-biofilm and Virulence Factor-Reducing Activities of Essential Oils and Oil Components as a Possible Option for Bacterial Infection Control

Abstract

Pathogenic biofilm-associated bacteria that adhere to biological or nonbiological surfaces are a big challenge to the healthcare and food industries. Antibiotics or disinfectants often fail in an attempt to eliminate biofilms from those surfaces. Based on selected experimental research, this review deals with the potential biofilm-inhibiting, virulence factor-reducing, and biofilm-eradicating activities of essential oils and single essential oil compounds using Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Chromobacterium violaceum as model organisms. In addition, for the bacteria reviewed in this overview, different essential oils and essential oil compounds were reported to be able to modulate the expression of genes that are involved in the formation of autoinducer molecules, biofilms, and virulence factors. The anti-quorum sensing activity of some essential oils and single essential oil compounds was demonstrated using the gram-negative bacterium C. violaceum. Reporter strains of this bacterium produce the violet-colored compound violacein whose synthesis is regulated by quorum sensing autoinducer molecules called acylhomeserinlactones. Of great interest was the discovery that enantiomeric monoterpenes affected the quorum sensing regulation system in different ways. While the (+)-enantiomers of carvone, limonene, and borneol increased violacein formation, their (−)-analogues inhibited violacein production.For the successful eradication of biofilms and the bacteria living inside them, it is absolutely necessary that the lipophilic volatile substances can penetrate into the aqueous channels of biofilms. As shown in recent work, hydrophilic nano-delivery systems encapsulating essential oils/essential oil compounds with antibacterial effects may contribute to overcome this problem.

Lemon Oils Attenuate the Pathogenicity of Pseudomonas aeruginosa by Quorum Sensing Inhibition

“…Concerning the motility controlled by QS, in concordance with our results, hydroalcoholic extracts (96% ethanol) from Citrus peels, including C. limon , C. medica and C. aurantium , reduced Campylobacter jejuni swarm motility (35–59%) [ 32 ].…”

“…Besides biofilm, extracellular virulence factors secretion also plays a vital role in the effective pathogenesis of P. aeruginosa . It was previously reported that some essential oils could interfere with the QS system regulation and the formation of virulence factors [ 31 , 32 ]. In line with this, the autoinducer production decreased between 26 and 55% in the lemon essential oils assayed; this result is similar to that found in grapefruit and mandarin essential oils [ 19 , 20 ].…”

Antiviral and Virucidal Properties of Essential Oils and Isolated Compounds – A Scientific Approach

“…on microbes such as bacteria or fungi [25]. It can therefore be assumed that this also applies to their antiviral activity.…”

“…2) and their oxygenated derivatives (alcohols, aldehydes, esters, ketones, phenols, and oxides) [13,[23][24][25]. Numerous in vitro and in vivo studies have shown that EOs and many of their individual EOCs exhibit different biological properties, for example, antibacterial [13,23,25], antifungal [13], antiviral [13], antioxidant [26,27], immunomodulatory [28,29], anti-inflammatory [24,27], and wound healing effects [30]. Due to their fat solubility, low molecular weight, and small size, the EOCs are able to pass through the skin, mucosa, and cell membranes and thus enter the systemic body circulation [13,24].…”

How well are we translating biofilm research from bench-side to bedside?

“…Ref. [ 8 , 9 ]), a quick search for biofilm or anti-biofilm products online, results in a long list of very questionable products that make outrageous claims. It would be a pity if the commercial biofilm arena were overtaken by these types of products, which would likely sour the public image of the biofilm problem and result in a downward trend in funding over the long-term.…”