|Posted on December 4, 2020 at 12:50 AM|
New agents that are effective against common pathogens are needed particularly for those resistant to conventional antimicrobial agents. Essential oils (EOs) are known for their antimicrobial activity. Using the broth microdilution method, we showed that (1) two unique blends of Cinnamomum zeylanicum, Daucus carota, Eucalyptus globulus and Rosmarinus officinalis EOs (AB1 and AB2; cinnamon EOs from two different suppliers) were active against the fourteen Gram‐positive and ‐negative bacteria strains tested, including some antibiotic‐resistant strains. Minimal inhibitory concentrations (MICs) ranged from 0.01% to 3% v/v with minimal bactericidal concentrations from <0.01% to 6.00% v/v; (2) a blend of Cinnamomum zeylanicum, Daucus carota, Syzygium aromaticum, Origanum vulgare EOs was antifungal to the six Candida strains tested, with MICs ranging from 0.01% to 0.05% v/v with minimal fungicidal concentrations from 0.02% to 0.05% v/v. Blend AB1 was also effective against H1N1 and HSV1 viruses. With this dual activity, against H1N1 and against S. aureus and S. pneumoniae notably, AB1 may be interesting to treat influenza and postinfluenza bacterial pneumonia infections. These blends could be very useful in clinical practice to combat common infections including those caused by microorganisms resistant to antimicrobial drugs.
Antimicrobial resistance poses a serious threat to the effective treatment of an ever‐increasing range of infections caused by bacteria, fungi and viruses. Worldwide, antibiotic resistance is increasing. For example, Escherichia coli, Klebsiella pneumoniae, Streptococcus pneumoniae have reported reduced antibiotic susceptibility, which exceeded 50% in most countries that provided data to the WHO Antimicrobial Resistance Global Report on Surveillance (WHO, 2014). Candidiasis has also become substantially problematic, with Candida albicans showing increased resistance to common antifungal agents (Goncalves, Souza, Chowdhary, Meis, & Colombo, 2016; Hawser & Douglas, 1995). The recent pandemic of a novel H1N1 influenza viral strain and emerging strains resistant to commonly used anti‐herpes simplex drugs also emphasizes the need to identify effective approaches to prevent and treat viral infections (Boivin, 2013; James & Prichard, 2014).
This increasing resistance has created a need to develop new antimicrobial agents. Essential oils (EOs) are good candidates as studies have shown that individual EOs and their isolated compounds, including terpenes and terpenoids (1,8‐cineole, carvacrol) and aromatic compounds (cinnamaldehyde and eugenol) have antimicrobial activity against a wide range of pathogens, with various spectrums of activity (Bassole & Juliani, 2012; Friedman, Henika, & Mandrell, 2002; Jantan, Karim Moharam, Santhanam, & Jamal, 2008). The antimicrobial effects of EOs are linked to their composition and cytotoxic effects, which cause cell membrane damage. EO compounds are lipophilic, and so pass through the cell wall and cytoplasmic membrane. They disrupt the structure of the polysaccharide, fatty acid, and phospholipid layers, making the membrane permeable (Bakkali, Averbeck, Averbeck, & Idaomar, 2008). Unfortunately, EOs do not specifically target pathogens; they can also affect eukaryotic cells in a reversible or irreversible manner (Carson, Hammer, & Riley, 2006). In extreme cases, EO cytotoxicity can lead to apoptosis, necrosis, and organ failure (Tisserand & Young, 2013). Therefore, EOs have to be used carefully, within the daily intake limits defined by the relevant authorities when available (EMEA and HMPC 2010, 2011; FAO and WHO 2003).
Three different EO blends were formulated, taking into account the specific activity of each. The first two (AB1 and AB2) contained EOs from Cinnamomum zeylanicum, Daucus carota, Eucalyptus globulus, and Rosmarinus officinalis, which differed only in that the cinnamon EOs were provided by two different suppliers. These EOs were selected for their antibacterial effects that had been observed, either individually or in pairs, in previously published studies (for review see Bassole & Juliani, 2012). Eucalyptus globulus and Cinnamomum Zeylanicum EOs also have been reported to have antiviral activity (Astani, Reichling, & Schnitzler, 2010; Cermelli, Fabio, Fabio, & Quaglio, 2008; Vimalanathan & Hudson, 2014). The third blend (AF) contained EOs from Cinnamomum zeylanicum, Daucus carota, Syzygium aromaticum, Origanum vulgare, which are known for their antifungal activity (Khan & Ahmad, 2011; Pinto, Vale‐Silva, Cavaleiro, & Salgueiro, 2009; Tavares et al., 2008; Zore, Thakre, Jadhav, & Karuppayil, 2011).
The antibacterial activity of AB1 and AB2 was evaluated in vitro against a selection of Gram‐positive and Gram‐negative bacteria, with or without antibiotic resistance, AB1 was evaluated for antiviral activity and AF was assessed for activity against different Candida strains.
Inxed for NIH by Dragonfly Kingdom Library https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5552930/
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