Identification of essential oils with activity against stationary phase Staphylococcus aureus

Abstract

Background Staphylococcus aureus is the most dominant human pathogen, responsible for a variety of chronic and severe infections. There is mounting evidence that persisters are associated with treatment failure and relapse of persistent infections. While some essential oils were reported to have antimicrobial activity against growing S. aureus, activity of essential oils against the stationary phase S. aureus enriched in persisters has not been investigated. Methods In this study, we evaluated the activity of 143 essential oils against both growing and stationary phase S. aureus by minimum inhibitory concentration (MIC) testing and by colony forming unit assay. Results We identified 39 essential oils (Oregano, Cinnamon bark, Thyme white, Bandit “Thieves”, Lemongrass (Cymbopogon flexuosus), Sandalwood oil, Health shield, Allspice, Amyris, Palmarosa, Cinnamon leaf, Clove bud, Citronella, Geranium bourbon, Marjoram, Peppermint, Lemongrass, Cornmint, Elemi, Ho wood, Head ease, Lemon eucalyptus, Litsea cubeba, Myrrh, Parsley seed, Coriander oil, Dillweed, Hyssop, Neroli, Rosewood oil, Tea tree, Cajeput, Clove bud, Lavender, Sleep tight, Vetiver, Palo santo, Sage oil, Yarrow) at 0.5% (v/v) concentration, 10 essential oils (Cinnamon bark, Oregano, Thyme white, Bandit “Thieves”, Lemongrass, Sandalwood oil, Health shield, Allspice, Amyris, Palmarosa at 0.25% (v/v) concentration, and 7 essential oils (Oregano, Cinnamon bark, Thyme white, Lemongrass, Allspice, Amyris, Palmarosa at 0.125% (v/v) concentration to have high activity against stationary phase S. aureus with no visible growth on agar plates after five-day exposure. Among the 10 essential oils which showed high activity at 0.25% (v/v) concentration, 9 (Oregano, Cinnamon bark, Thyme white, Bandit “Thieves”, Lemongrass, Health shield, Allspice, Palmarosa, Amyris showed higher activity than the known persister drug tosufloxacin, while Sandalwood oil had activity at a higher concentration. In Oregano essential oil combination studies with antibiotics, Oregano plus tosufloxacin (or levofloxacin, ciprofloxacin) and rifampin completely eradicated stationary phase S. aureus cells, but had no apparent enhancement for linezolid, vancomycin, sulfamethoxazole, trimethoprim, azithromycin or gentamicin. Conclusions Our findings indicate that some essential oils have excellent activity against both growing and stationary phase S. aureus. Further studies are needed to identify the active components, evaluate safety, pharmacokinetics, and their activity to eradicate S. aureus infections in vivo.

In Vitro Antimicrobial Activity of Thymus vulgaris, Origanum vulgare, Satureja montana and Their Mixture against Clinical Isolates Responsible for Canine Otitis Externa

“…Oregano, savory, and thyme EOs were active against the tested Staphylococcus isolates in agreement with data reported by other investigations [ 3 , 29 , 30 , 31 , 32 , 33 ]. Low MIC values were found when testing the isolates against the three EOs; moreover, the sensitivity of Staphylococcus spp.…”

Nanoemulsion and Nanogel Containing Eucalyptus globulus Essential Oil; Larvicidal Activity and Antibacterial Properties

“…Furthermore, some studies have been published on the antibacterial effects of eucalyptus extract on E. coli , S. aureus, and P. fluorescens [ 45 – 47 ]. Besides, it has been confirmed that inhaling eucalyptus extracts benefit non/infectious respiratory disorders, such as bronchitis, asthma, and chronic obstructive pulmonary disease [ 48 , 49 ]. Moreover, EGEO is an immune stimulant with antiinflammatory, antioxidant, and analgesic effects [ 48 , 49 ].…”

“…Besides, it has been confirmed that inhaling eucalyptus extracts benefit non/infectious respiratory disorders, such as bronchitis, asthma, and chronic obstructive pulmonary disease [ 48 , 49 ]. Moreover, EGEO is an immune stimulant with antiinflammatory, antioxidant, and analgesic effects [ 48 , 49 ]. Some reports on its nanoformulated states were also reported.…”

Antimicrobial Activity of Essential Oils Evaluated In Vitro against Escherichia coli and Staphylococcus aureus

“…EOs display different biological properties, such as anti-inflammatory, sedative, digestive, antimicrobial, antiviral, or antioxidant activities [9,10], and have been widely employed as excellent substitutes for chemical-based preservatives. Previous studies confirmed the antibacterial action of EOs against S. aureus [11], Enterobacter aerogenes, Klebsiella oxytoca, Proteus mirabilis, Morganella morganii and E. coli [12]. Moreover, bactericidal activity and the ability of EOs to interfere with bacterial replication have prompted their use in the pharmaceutical, health, cosmetic, agricultural, and food industries [13].…”