An upcycled fraction of Melaleuca alternifolia essential oil regenerates the skin through the skin melatonin pathway and improves sleep quality

BACKGROUND

Sleep is one of the most important factors affecting overall health. During the night, the skin repairs damage caused by daily stresses. Melatonin plays a key role in this process. Toxins are removed, and cellular repair and growth hormone production are increased. Inter alia, this also decreases signs of intrinsic aging.

AIMS

The current study was intended to demonstrate the impact of a unique fraction of Melaleuca alternifolia (FMA) essential oil, on sleep and skin quality.

METHODS

The effect of FMA was investigated in vitro on skin cells, evaluating its antioxidant and anti-inflammatory properties, and in an ex-vivo study on human skin biopsies treated with FMA following stress induction. In addition, two clinical studies were performed on volunteers with life-style-related sleep complaints. In one study, sleep was measured using a noncontact monitoring device (SleepScore Labs, Max). A second study was conducted to assess skin anti-aging effects.

RESULTS

In vitro application of FMA reduced IL-8 and reactive oxygen species (ROS) generation in skin cells. This was confirmed ex vivo through a decrease in inflammatory markers and an increase in antioxidant enzymes after stress induction. Interestingly, FMA also upregulated melatonin-associated genes. Real-world sleep tracking revealed that FMA significantly improved sleep quality, relative to unscented control. In vivo applications also showed a reduction in signs of aging.

CONCLUSION

These results provide initial data to suggest that this unique FMA delivers skin anti-aging benefits via a two-pronged mode of action, improving sleep quality, and reducing skin inflammatory and oxidative stress.

Nanoemulsions and nanocapsules loaded with Melaleuca alternifolia essential oil for sepsis treatment

Sepsis represents a complex clinical syndrome that results from a harmful host response to infection. The infections most associated with sepsis are pneumonia, intra-abdominal infection, and urinary tract infection. Tea tree oil (TTO) has shown high antibacterial activity; however, it exhibits low aqueous solubility and high volatility, which have motivated its nanoencapsulation. In this study, the performance of nanoemulsions (NE) and nanocapsules (NC) loaded with TTO was compared. These systems were prepared by spontaneous emulsification and nanoprecipitation methods, respectively. Poly-ε-caprolactone or Eudragit® RS100 were tested as polymers for NCs whereas Tween® 80 or Pluronic® F68 as surfactants in NE preparation. Pluronic® F68 and Eudragit® RS100 resulted in more homogeneous and stable nanoparticles. In accelerated stability studies at 4 and 25 °C, both colloidal suspensions (NC and NE) were kinetically stable. NCs showed to be more stable to photodegradation and less cytotoxic than NEs. After sepsis induction by the cecal ligation and puncture (CLP) model, both NE and NC reduced neutrophil infiltration into peritoneal lavage (PL) and kidneys. Moreover, the systems increased group thiols in the kidney and lung tissue and reduced bacterial growth in PL. Taken together, both systems showed to be effective against injury induced by sepsis; however, NCs should be prioritized due to advantages in terms of cytotoxicity and physicochemical stability.

The essential oil of Melaleuca alternifolia incorporated into hydrogel induces antimicrobial and anti-inflammatory effects on infected wounds by Staphylococcus aureus

Staphylococcus aureus is one of the most common bacterial isolates found in wounds. Thus, innovative dressings, such as hydrogels, are interesting vehicles for incorporating bioactive compounds like those from Melaleuca alternifolia essential oil (MaEO). In this study, we evaluated the antimicrobial and anti-inflammatory potential of MaEO incorporated into an alginate and chitosan hydrogel for treating wounds infected by S. aureus. The hydrogel incorporated with MaEO 1% (HMa 1%) was homogeneous with a bright pale-yellow color and the characteristic smell of Melaleuca. The incorporation of MaEO 1% does not affect the stability of the hydrogel, which was stable up to 90 days of storage. The Scanning electron microscopy analysis revealed that hydrogels showed irregular surfaces and interconnected porous structures with accumulations of oil crystals distributed throughout the formulation. HMa 1% has a high moisture content (95.1%) and can absorb simulated wound fluid. Regarding the antimicrobial effects, HMa 1% reduced the growth of S. aureus ATCC 6538 in both in vitro conditions and in an ex vivo model of wounds using porcine skin. In addition, the dairy topical treatment of murine skin lesions with HMa 1% induced a significant reduction of the wound area, inflammation score, and bacterial load, as well as tissue re-epithelialization and modulation of inflammatory mediators. Therefore, hydrogel incorporated with MaEO 1% has excellent potential to be used in the pharmacotherapy of infected wounds.

Effect of cationic surfactant on the physicochemical and antibacterial properties of colloidal systems (emulsions and microemulsions)

Colloidal systems have been used to encapsulate, protect and release essential oils in mouthwashes. In this study, we investigated the effect of cetylpyridinium chloride (CPC) on the physicochemical properties and antimicrobial activity of oil-in-water colloidal systems containing tea tree oil (TTO) and the nonionic surfactant polysorbate 80. Our main aim was to evaluate whether CPC could improve the antimicrobial activity of TTO, since this activity is impaired when this essential oil is encapsulated with polysorbate 80. These systems were prepared with different amounts of TTO (0-0.5% w/w) and CPC (0-0.5% w/w), at a final concentration of 2% (w/w) polysorbate 80. Dynamic light scattering (DLS) results revealed the formation of oil-swollen micelles and oil droplets as a function of TTO concentration. Increases in CPC concentrations led to a reduction of around 88% in the mean diameter of oil-swollen micelles. Although this variation was of only 20% for the oil droplets, the samples appearance changed from turbid to transparent. The surface charge of colloidal structures was also markedly affected by the CPC as demonstrated by the transition in zeta potential from slightly negative to highly positive values. Electron paramagnetic resonance (EPR) studies showed that this transition is followed by significant increases in the fluidity of surfactant monolayer of both colloidal structures. The antimicrobial activity of colloidal systems was tested against a Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureaus) bacteria. Our results revealed that the inhibition of bacterial growth is observed for the same CPC concentration (0.05% w/w for E. coli and 0.3% w/w for S. aureus) regardless of TTO content. These findings suggest that TTO may not act as an active ingredient in polysorbate 80 containing mouthwashes.

Effect of Tea Tree Oil Addition to Denture Liners Against Candida albicans and Bond Strength to Acrylic Denture Bases

PURPOSE

To evaluate the effect of adding tea tree oil to denture liners on Candida albicans and bond strength to the acrylic denture base.

MATERIALS AND METHODS

Disc-shaped specimens were fabricated from silicone-based resilient liner (Tokuyama, Molloplast), acrylic-based hard liner (GC Reline), and acrylic-based soft liner (Visco-gel). Tea tree oil (TTO) was incorporated into the liners at varying concentrations (0% [control], 2%, 5%, 8%). C albicans were counted by viable colony count, and optical density (OD) was measured with a spectrophotometer. The tensile strength to heat polymerized acrylic denture base was measured in a universal testing machine. The compliance of the data to the distribution of normality was evaluated using the Shapiro Wilk test. Two-way ANOVA, Bonferroni correction, and paired sample t test were performed (α = .05).

RESULTS

The addition of TTO into liners provided a significant decrease in the OD values (P < .001). The control groups of the liners presented the highest colony counts, whereas increasing TTO decreased the results (P < .01). According to tensile bond strength test, 8% TTO addition resulted in a significant decrease for Tokuyama (P < .01) and Molloplast liners (P < .05), while 2% TTO resulted in significance for GC Reline (P < .001).

CONCLUSIONS

Denture liners containing increasing percentages of TTO presented lower amounts of C albicans colonies and decreased bond strength to the denture bases. When using TTO for its antifungal properties, the amount added should be carefully selected because the tensile bond strength may be affected.

Nanoemulsions (O/W) prepared from essential oil extracted from Melaleuca alternifolia: synthesis, characterization, stability and evaluation of anticancerous, anti-oxidant, anti-inflammatory and antidiabetic activities

Essential oil from Melaleuca alternifolia (also known as Tea tree essential oil, TTO) is used as traditional medicine and used as therapeutic in medicine, food and cosmetic sectors. However, this oil is highly unstable, volatile and prone to oxidation which limits its practical use. The objective of this study was synthesis of tea tree oil based O/W (oil/water) nanoemulsions (tea tree essential oil nanoemulsions, TNE) and evaluation of its biological potential. Physiological characterization was carried out using UV, fluorescent, and FT-IR techniques. Various biological activities such as anticancerous, antidiabetic and anti-inflammatory were also estimated. Pharmacokinetics study on TNE was carried out. Encapsulation efficiency of nanoemulsions was found to be 83%. Nanoemulsions were spherical in shape with globule size 308 nm, zeta potential -9.42 and polydispersity index was 0.31. Nanoemulsions were stable even after 50 days of storage at different temperatures. Anti-oxidant potential of TNE was conducted by various assays and IC50 were: Nitric oxide radical scavenging activity:225.1, DPPH radical scavenging activity:30.66, Iron chelating assay:38.73, and Iron reducing assay:39.36. Notable anticancer activity was observed with the percent cell viability of HeLa cells after treatment with 1, 2 and 5 µl of TNE was 82%, 41% and 24%, respectively. Antidiabetic study revealed that TNE inhibited -amylase in a dose-dependent manner, with 88% inhibition at its higher volume of 250 µl. Drug kinetic study revealed that nanoemulsions exhibited first-order model. Based on this, the possible role of M. alternifolia oil-based nanoemulsions in cosmetic, food, and pharma sectors has been discussed.

Comparison of chitosan and SLN nano-delivery systems for antibacterial effect of tea tree (Melaleuca alternifolia) oil against P. aeruginosa and S. aureus

Treatment of wounds is challenging due to bacterial infections, including Staphylococcus aureus and Pseudomonas aeruginosa. Using the merits of alternative antimicrobials like tea tree oil (TTO) and nanotechnology, they can be helpful in combatting bacterial infections. Solid lipid nanoparticle (SLN) and chitosan (CS) nanoparticles show great potential as carriers for enhancing the stability and therapeutic benefits of oils. The aim of this study is to compare the influence of nanocarriers in enhancing the antibacterial effects of TTO. The study evaluates the physicochemical and antibacterial properties of TTO-SLN and TTO-CS against P. aeruginosa and S. aureus. The TTO-SLN nanoparticles showed a clear round shape with the average diameter size of 477 nm, while the TTO-CS nanoparticles illustrated very homogeneous morphology with 144 nm size. The encapsulation efficiency for TTO-CS and TTO-SLN was ∼88.3% and 73.5%, respectively. Minimum inhibitory concentration against S. aureus and P. aeruginosa for TTO-CS, TTO-SLN, and pure TTO were 35 and 45 µg ml-1, 130 and 170 µg ml-1, and 380 and 410 µg ml-1, respectively. Since TTO-CS revealed an impressively higher antimicrobial effects in comparison with TTO-SLN and TTO alone, it can be considered as a nanocarrier that produces the same antimicrobial effects with lower required amounts of the active substance.

Effects of adding tea tree oil on growth performance, immune function, and intestinal function of broilers

The aim of this study was to investigate the effects of adding tea tree oil (TTO) in the basal diet on growth performance, immune function, and intestinal function in broilers. This study utilized 1,650 one-day-old broilers with good health and similar body weight. Subjects were randomized into 5 groups with 6 replicates each: the control group (CON, basal diet), positive control group (PCG, basal diet + 100 mg/kg oregano oil in diet), low-dose TTO group (TTO-L, 50 mg/kg TTO added in the basal diet), medium-dose TTO group (TTO-M, 100 mg/kg TTO added in the basal diet), and high-dose TTO group (TTO-H, 200 mg/kg TTO added in the basal diet). The whole test period lasted 28 d. The results showed that the broilers fed with TTO supplemented diet had significantly higher body weight and average daily gain (ADG) (P = 0.013), and had a lower feed conversion ratio (F/G) (P = 0.010) throughout the trial period. The index of thymus in TTO-M increased significantly compared to CON (P = 0.015) on d 28. On d 14 and 28, C3, IFN-γ, TNF-α, and IL-2 levels in TTO-L serum were significantly increased (P < 0.001); the 3 test groups supplemented with TTO had significantly higher titers of avian influenza H9 subtype in their serum (P < 0.05). Tea tree oil supplement in the diet also had a positive and significant effect on the intestinal morphology of broilers throughout the experiment (P < 0.05). These results indicate that TTO has the ability to promote broiler growth, regulate immunity, and improve intestinal morphology. The proposed dosage of adding 50 mg/kg in broiler basal diets provides a theoretical basis for its subsequent use in livestock feeds.

Antimicrobial and antibiofilm effects of shikonin with tea tree oil nanoemulsion against Candida albicans and Staphylococcus aureus

The current work aims to develop a shikonin and tea tree oil loaded nanoemulsion system stabilized by a mixture of GRAS grade surfactants (Tween 20 and monoolein) and a cosurfactant (Transcutol P). This system was designed to address the poor aqueous solubility and photostability issues of shikonin. The authenticity of shikonin employed in this study was confirmed using nuclear magnetic resonance (NMR) spectroscopy. The optimized nanoemulsion exhibited highly favorable characteristics in terms of zeta potential (-23.8 mV), polydispersity index (0.216) and particle size (22.97 nm). These findings were corroborated by transmission electron microscopy (TEM) micrographs which confirmed the spherical and uniform nature of the nanoemulsion globules. Moreover, attenuated total reflectance (ATR) and X-ray diffraction analysis (XRD) analysis affirmed improved chemical stability and amorphization, respectively. Photodegradation studies were performed by exposing pure shikonin and the developed nanoemulsion to ultraviolet light for 1 h using a UV lamp, followed by high performance liquid chromatography (HPLC) analysis. The results confirmed that the developed nanoemulsion system imparts photoprotection to pure shikonin in the encapsulated system. Furthermore, the research investigated the effect of the nanoemulsion on biofilms formed by Candida albicans and methicillin resistant Staphylococcus aureus (MRSA). Scanning electron microscopy, florescence microscopy and phase contrast microscopy unveiled a remarkable reduction in biofilm area, accompanied by disruptions in the cell wall and abnormalities on the cell surface of the tested microorganisms. In conclusion, the nanoencapsulation of shikonin with tea tree oil as the lipid phase showcased significantly enhanced antimicrobial and antibiofilm potential compared to pure shikonin against resistant strains of Candida albicans and Staphylococcus aureus.

Evaluation of a novel treatment, selenium disulfide, in killing Demodex folliculorum in vitro

OBJECTIVE

To evaluate the effectiveness of varying concentrations of selenium sulfide, an active ingredient in antidandruff shampoo, in killing Demodex folliculorum.

METHODS

Sixty-five eyelashes with live Demodex from 29 patients seen at the Nassau University Medical Center (17 patients) and Ophthalmic Consultants of Long Island (12 patients) were observed under light microscopy for 90 minutes in 0.1%, 0.5%, 1.0%, and 4% selenium sulfide with either carboxymethyl cellulose (CMC) solution or petroleum jelly ointment (Vaseline, Unilever, London) as excipients. Positive and negative controls also were evaluated as separate solutions of CMC, petroleum jelly, basic saline solution, 50% tea tree oil, and 100% tea tree oil. The number of Demodex deaths and time of death were recorded.

RESULTS

Demodex deaths in the selenium sulfide reagents were observed in the 4% selenium sulfide solution with CMC (36.4% kill rate, 4 of 11 Demodex, average time of death 17.5 minutes, p = 0.038) and 4% selenium sulfide with petroleum jelly ointment (12.5% kill rate, 1 of 8 Demodex, time of death 75 minutes, p = 0.351). No Demodex deaths were witnessed in the other selenium sulfide treatment groups. All Demodex died in the 50% and 100% tea tree oil positive control group.

CONCLUSIONS

Selenium sulfide has shown efficacy in killing Demodex at a 4% concentration with the CMC solution and mild activity with 4% petroleum jelly. More research on selenium sulfide solutions at higher concentrations is indicated.

Tea Tree Essential Oil Kills Escherichia coli and Staphylococcus epidermidis Persisters

Persister cells are a small subpopulation of non-growing bacteria within a population that can survive long exposures to antibiotic treatment. Following antibiotic removal, persister cells can regrow and populate, playing a key role in the chronic reoccurrence of bacterial infections. The development of new molecules and methods to kill bacterial persisters is critical. Essential oils and other natural products have long been studied for their antimicrobial effects. Here, we studied the effectiveness of tea tree essential oil (TTO), a common component in many commercial care products, against Escherichia coli and Staphylococcus epidermidis persister cells. Using biphasic kill curve assays, we found that concentrations of 0.5% and 1.0% TTO for E. coli and S. epidermidis, respectively, completely eradicated persister cells over a period of 24 h, with the component terpinen-4-ol responsible for most of the killing. Using a colorimetric assay, it was determined that the TTO exhibited its anti-persister effects through a membrane disruption mechanism.

Fabrication and Biological Activities of All-in-One Composite Nanoemulsion Based on Blumea balsamifera Oil-Tea Tree Oil

Nanoemulsion is a new multi-component drug delivery system; the selection of different oil phases can give it special physiological activity, and play the role of "medicine and pharmaceutical excipients all-in-one". In this paper, we used glycyrrhizic acid as the natural surfactant, and Blumea balsamifera oil (BB) and tea tree oil (TTO) as the mixed oil phase, to obtain a new green functional composite nanoemulsion. Using the average particle size and polydispersion index (PDI) as the evaluation criteria, the effects of the oil ratio, oil content, glycyrrhizic acid concentration, and ultrasonic time on the nanoemulsion were systematically investigated. The stability and physicochemical properties and biological activities of BB-TTO NEs prepared via the optimum formulation were characterized. The optimal prescription was BB: TTO = 1:1, 5% oil phase, 0.7% glycyrrhizic acid, and 5 min ultrasonication time. The mean particle size, PDI, and zeta potential were 160.01 nm, 0.125, and -50.94 mV, respectively. The nanoemulsion showed non-significant changes in stability after centrifugation, dilution, and 120 days storage. These nanoemulsions were found to exhibit potential antibacterial and anti-inflammatory activities. The minimal inhibitory concentration (MIC) of BB-TTO NEs against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa is 2975 μg/mL, 2975 μg/mL, and 5950 μg/mL, respectively. A lower level of inflammatory cell infiltration and proportion of fibrosis were found in the synovial tissue of AIA rats treated with BB-TTO NEs. These findings demonstrate that the BB-TTO NEs produced in this study have significant potential for usage in antibacterial and anti-inflammatory areas.

The synergy of tea tree oil nano-emulsion and antibiotics against multidrug-resistant bacteria

AIMS

We determined the synergistic effects of tea tree essential oil nano-emulsion (nanoTTO) and antibiotics against multidrug-resistant (MDR) bacteria in vitro and in vivo. Then, the underlying mechanism of action of nanoTTO was investigated.

METHODS AND RESULTS

Minimum inhibitory concentrations and fractional inhibitory concentration index (FICI) were determined. The transepithelial electrical resistance (TEER) and the expression of tight junction (TJ) protein of IPEC-J2 cells were measured to determine the in vitro efficacy of nanoTTO in combination with antibiotics. A mouse intestinal infection model evaluated the in vivo synergistic efficacy. Proteome, adhesion assays, quantitative real-time PCR, and scanning electron microscopy were used to explore the underlying mechanisms. Results showed that nanoTTO was synergistic (FICI ≤ 0.5) or partial synergistic (0.5 < FICI < 1) with antibiotics against MDR Gram-positive and Gram-negative bacteria strains. Moreover, combinations increased the TEER values and the TJ protein expression of IPEC-J2 cells infected with MDR Escherichia coli. The in vivo study showed that the combination of nanoTTO and amoxicillin improved the relative weight gain and maintained the structural integrity of intestinal barriers. Proteome showed that type 1 fimbriae d-mannose specific adhesin of E. coli was downregulated by nanoTTO. Then, nanoTTO reduced bacterial adhesion and invasion and inhibited the mRNA expression of fimC, fimG, and fliC, and disrupted bacterial membranes.

The healing effect of topical tea tree oil on pressure ulcers in a rat model

Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated. Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs. Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin). Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.

The healing effect of topical tea tree oil on pressure ulcers in a rat model

Objective: The effects of topical tea tree oil (TTO) on the healing of pressure ulcers (PUs) in an animal model was evaluated. Method: To induce PUs, ischaemia-reperfusion cycles were performed by the external application of magnetic plates, with an ischaemic period of eight hours and a reperfusion period of 16 hours. Male and female Wistar rats were divided into three equally sized groups (n=20): one group received topical glycerin twice daily, another group received topical 10% (volume/volume (v/v)) TTO in glycerin twice daily; and the remaining group was untreated. The animals were assessed after one, four, seven and 14 cycles of ischaemia-reperfusion by thermal camera imaging, and then euthanised and sampled to investigate the degree of inflammation, collagen synthesis and apoptosis in the PUs. Results: Although topical glycerin alone suppressed local inflammation and apoptosis, this suppressive effect was accentuated at all timepoints by the application of topical TTO + glycerin. Similarly, an increase in collagen synthesis was observed in the glycerin group and this was accentuated by TTO at all timepoints. Parallel to the histological findings, the local temperature had decreased significantly on days 4 and 7 for both treatment groups (glycerin and TTO+glycerin). Conclusion: In this study, treatment with 10% (v/v) TTO in glycerin effectively suppressed skin inflammation and apoptosis, while it increased collagen synthesis during PU formation.

Nanolipogel Loaded with Tea Tree Oil for the Management of Burn: GC-MS Analysis, In Vitro and In Vivo Evaluation

The GC-MS analysis of tea tree oil (TTO) revealed 38 volatile components with sesquiterpene hydrocarbons (43.56%) and alcohols (41.03%) as major detected classes. TTO efficacy is masked by its hydrophobicity; nanoencapsulation can address this drawback. The results showed that TTO-loaded solid lipid nanoparticles (SLN1), composed of glyceryl monostearate (2% w/w) and Poloxamer188 (5% w/w), was spherical in shape with a core-shell microstructure. TTO-SLN1 showed a high entrapment efficiency (96.26 ± 2.3%), small particle size (235.0 ± 20.4 nm), low polydispersity index (0.31 ± 0.01), and high negative Zeta potential (−32 mV). Moreover, it exhibited a faster active agent release (almost complete within 4 h) compared to other formulated TTO-SLNs as well as the plain oil. TTO-SLN1 was then incorporated into cellulose nanofibers gel, isolated from sugarcane bagasse, to form the ‘TTO-loaded nanolipogel’ which had a shear-thinning behavior. Second-degree thermal injuries were induced in Wistar rats, then the burned skin areas were treated daily for 7 days with the TTO-loaded nanolipogel compared to the unmedicated nanolipogel, the TTO-loaded conventional gel, and the normal saline (control). The measurement of burn contraction proved that TTO-loaded nanolipogel exhibited a significantly accelerated skin healing, this was confirmed by histopathological examination as well as quantitative assessment of inflammatory infiltrate. This study highlighted the success of the proposed nanotechnology approach in improving the efficacy of TTO used for the repair of skin damage induced by burns.

Antibacterial, anti-biofilm, and anti-virulence potential of tea tree oil against leaf blight pathogen Xanthomonas oryzae pv. oryzae instigates disease suppression

Bacterial leaf blight (BLB) disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), causes major annual economic losses around the world. Inorganic copper compounds and antibiotics are conventionally used to control BLB disease. They often cause environmental pollution, contributing to adverse effects on human health. Therefore, research is now leading to the search for alternative control methods. Tea tree oil (TTO) is obtained from a traditional medicinal plant, Melaleuca alternifolia, with antibacterial properties. In this study, we found that TTO showed antibacterial activity against Xoo with a minimum inhibitory concentration (MIC) of 18 mg/ml. These antagonistic activities were not limited only to planktonic cells, as further studies have shown that TTO effectively eradicated sessile cells of Xoo in both initial and mature biofilms. Furthermore, it was also observed that TTO reduced various key virulence properties of Xoo, such as swimming, swarming motility, and the production of extracellular polymeric substances, xanthomonadin, and exoenzymes. TTO triggered ROS generation with cell membrane damage as an antibacterial mode of action against Xoo. The in silico study revealed that 1,8-cineole of TTO was effectively bound to two essential proteins, phosphoglucomutase and peptide deformylase, responsible for the synthesis of EPS and bacterial survival, respectively. These antibacterial and anti-virulence activities of TTO against Xoo were further confirmed by an ex vivo virulence assay where TTO significantly reduced the lesion length caused by Xoo on rice leaves. All these data concluded that TTO could be a safe, environment-friendly alternative approach for the comprehensive management of BLB disease.

Exploring the antibacterial, antibiofilm, and antivirulence activities of tea tree oil-containing nanoemulsion against carbapenem-resistant Serratia marcescens associated infections

Carbapenem-resistant Serratia marcescens (CRE-S. marcescens) has recently emerged as an opportunistic human pathogen that causes various nosocomial and respiratory tract infections. The prognosis for CRE-S. marcescens-related infections is very poor and these infections are difficult to treat. This study investigated the synthesis of tea tree oil nanoemulsion (TTO-NE) and its impact on CRE-S. marcescens both in vitro and in vivo. TTO-NE was characterized by dynamic light scattering (DLS) and effectively eradicated bacterial planktonic and sessile forms, reduced bacterial virulence factors, and generated reactive oxygen species (ROS) in the bacterial cell. Notably, TTO-NE was efficient in reducing the colonization of CRE-S. marcescens in a C. elegans in vivo model. The data suggest that TTO-NE might be an excellent tool to combat infections associated with CRE-S. marcescens.

Evaluation of the antibacterial effect of tea tree oil on Enterococcus faecalis and biofilm in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Tea tree essential oil (TTO) is extracted from the leaves of Melaleuca alternifolia by steam distillation. It is well known for its traditional medicinal uses, particularly for the treatment of bruises, insect bites, skin infections, vertigo, convulsions, toothache, and rheumatism. Earlier research has shown that TTO can effectively inhibit oral microorganisms in the root canals. Enterococcus faecalis (E. faecalis) has been considered to be associated with persistent root canal infections and root canal treatment failure. The biofilm of E. faecalis makes it more vigorous, toxic, and resistant to antibiotics.

AIM OF THE STUDY

In this study, our aim was to evaluate the antimicrobial effects of TTO on planktonic E. faecalis and biofilms compared with 0.2% CHX.

MATERIALS AND METHODS

We explored the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC), the bacteriostatic rate by MTT assay, the antimicrobial time by time-kill assay, and the effects on cell integrity, the biomass, and bacterial activity of E. faecalis biofilms. Finally, we investigated the microstructure changes of E. faecalis biofilms using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS

The MIC and MBC values were 0.25% and 0.5%, the bacterial inhibition rate, time-kill was dosage dependent, and TTO can effectively destroy membrane integrity. SEM CLSM images revealed that TTO could reduce bacterial aggregation, biofilm thickness and inhibited biofilm formation. The effect of TTO was the same as that of 0.2% CHX at some specific concentrations. In summary, TTO has the potential to be effective against E. faecalis infections.

CONCLUSIONS

TTO was able to inhibit E. faecalis by destroying cell membrane, inhibiting the formation of E. faecalis biofilms, and eliminating mature formed biofilms. In this study, TTO has the potential to be further developed as a novel antibacterial drug.

Antimicrobial and hand hygiene effects of Tea Tree Essential Oil disinfectant: A randomised control trial

BACKGROUND

Hand hygiene is paramount in preventing healthcare-associated infections in medical environments and the spread of infectious diseases in non-medical environments.

AIMS

This study used a randomised controlled trial to investigate the effects of a tea tree (Melaleuca alternifolia) oil disinfectant on hand disinfection and skin condition.

METHODS

A tea tree oil group received 5 mL of 10% tea tree oil disinfectant mixed in a ratio of 2:2:1:15 of Melaleuca alternifolia oil, solubiliser, glycerin and sterile distilled water. Data collection took place between April 9 and April 13, 2018. The subjects were 112 healthy adults. An alcohol group received 2 mL of a gel-type hand sanitiser comprising 83% ethanol used without water; a benzalkonium chloride group received 0.8 mL of a foam-type hand sanitiser containing benzalkonium chloride used without water and a control group received no treatment. Subjective skin condition, transepidermal water loss and adenosine triphosphate were assessed, and a microbial culture test was performed following treatment.

RESULTS

The general characteristics and the pretreatment dependent variables did not differ significantly by group. Posttreatment adenosine triphosphate log₁₀ values significantly differed across all four groups (F = 3.23, P = .025). Similarly, posttreatment bacterial density log₁₀ values differed significantly across the tea tree oil, alcohol, benzalkonium chloride and control groups (F = 91.71, P < .001).

CONCLUSION

The study confirmed that tea tree oil disinfectant is effective for hand disinfection. Accordingly, tea tree oil disinfectants may be introduced to nursing practice as a new hand hygiene product to prevent and reduce healthcare-associated infections.

Rosin modified aminated mesoporous silica adsorbed tea tree oil sustained-release system for improve synergistic antibacterial and long-term antibacterial effects

Tea tree oil, a natural antibacterial compound, cannot be used effectively because of its volatile nature. In this work, a biocompatible carrier was prepared and loaded with tea tree essential oil. The carrier was prepared via the electrostatic or chemical action of aminated mesoporous silica and sodium rosin for achieving a low volatilization rate of tea tree essential oil. A synergistic antibacterial effect was observed between sodium rosin and tea tree essential oil. This method utilized the positive charge of the amino group and the condensation reaction with the carboxyl group to achieve physical and chemical interactions with sodium rosin. Fourier Transform Infrared, Brunauer-Emmet-Teller, Zeta potential, SEM, TEM, and TG were performed to characterize the structure and properties of the samples. Compared to the electrostatic effect, the chemically modified system exhibited a longer sustained release, and the sustained release curve followed the Korsmeyer-Peppas release model. Also, the antibacterial properties of the chemically modified system exhibited better minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) respectively, the MIC and MBC forE. coliwere 0.3 mg ml^-1and 0.6 mg ml^-1respectively, forS. aureuswere 0.15 mg ml^-1and 0.3 mg ml^-1respectively. More strikingly, the sample also demonstrated long-term antibacterial performance. Therefore, this work provides a new way for the delivery of volatile antibacterial drugs to achieve sustained-release and long-lasting antibacterial effects.

Antifungal Activity of Melaleuca alternifolia Essential Oil (TTO) and Its Synergy with Itraconazole or Ketoconazole against Trichophyton rubrum

Over the past 20–30 years, Trichophyton rubrum represented the most widespread dermatophyte with a prevalence accounting for 70% of dermatophytosis. The treatment for cutaneous infections caused by Trichophyton spp. are imidazoles (ketoconazole (KTZ)) and triazoles (itraconazole (ITZ)). T. rubrum can develop resistance to azoles after prolonged exposure to subinhibitory concentrations resulting in therapeutic failures and chronic infections. These problems have stimulated the search for therapeutic alternatives, including essential oils, and their potential use in combination with conventional antifungals. The purpose of this study was to evaluate the antifungal activity of tea tree oil (TTO) (Melaleuca alternifolia essential oil) and the main components against T. rubrum and to assess whether TTO in association with KTZ/ITZ as reference drugs improves the antifungal activity of these drugs. We used a terpinen-4-ol chemotype (35.88%) TTO, and its antifungal properties were evaluated by minimum inhibitory and minimum fungicidal concentrations in accordance with the CLSI guidelines. The interaction between TTO and azoles was evaluated through the checkerboard and isobologram methods. The results demonstrated both the fungicide activity of TTO on T. rubrum and the synergism when it was used in combination with azoles. Therefore, this mixture may reduce the minimum effective dose of azole required and minimize the side effects of the therapy. Synergy activity offered a promise for combination topical treatment for superficial mycoses.

Associating chitosan and microemulsion as a topical vehicle for the administration of herbal medicines

A viscous solution of low molecular weight chitosan (CH) at 5% w/v (10.2 kDa, 75 % deacetylated, 1451 cP at 25 °C) was associated with a microemulsion (ME) that undergoes a phase transition after water absorption in situ (≈28 % w/w), forming a more viscous liquid crystal, which was potentially evaluated as a topical vehicle. The ME was selected from a phase diagram, selecting a composition based on Tween® 80 (52 %), myristate isopropyl (28 %), and the aqueous phase (water and polyethylene glycol 400, 60:40 w/w) (20 %), which was after replaced by CH and herbal medicines (HM). HM are alternatives to treat candidiasis, and Stryphnodendron adstringens shell extract, characterized by molecular networking, and Melaleuca alternifolia Chell essential oil (46 % of terpinen-4-ol), showed in vitro activity against Candida albicans. Associating CH in ME improved the mechanical properties of the topical formulation, as adhesiveness, which is an advantageous feature for the topical treatment of vulvovaginal candidiasis.

Terpinen-4-ol Enhances Disease Resistance of Postharvest Strawberry Fruit More Effectively than Tea Tree Oil by Activating the Phenylpropanoid Metabolism Pathway

This study aimed to reveal the effects and possible mechanism of terpinen-4-ol, the main component of tea tree oil (TTO), on the disease resistance of strawberry fruit. When the effects of TTO and its components were compared on the decay development in fruit inoculated with Botrytis cinerea after treatment, strawberry treated with terpinen-4-ol showed the lowest disease incidence (44.4%) after 48 h and also the smallest lesion diameter during the whole storage. This indicates that terpinen-4-ol induces the highest disease resistance in strawberry compared with TTO and other components. Untargeted metabolomic analysis showed that terpinen-4-ol treatment strongly activated phenylpropanoid biosynthesis and flavonoid metabolism pathway by increasing the accumulation of cinnamaldehyde, coniferyl aldehyde, naringenin, taxifolin, quercetin, and quercitrin in fruit at 12 h after treatment. In addition, terpinen-4-ol treatment also caused the accumulation of total phenolics and lignin by enhancing activities and relative gene expression of key enzymes in the phenylpropanoid metabolism pathway. These results suggest that terpinen-4-ol, as the key component of TTO, is the most important contributor to the effectiveness of TTO in improving disease resistance of strawberry fruit through activating the phenylpropanoid metabolism pathway.

Comparative study between topically applied irradiated human amniotic membrane in combination with tea tree oil versus topical tioconazole in pityraisis versicolor treatment

Pityriasis versicolor (PV) is a chronic skin disease caused by virulence activities of Malassezia, a genus of skin-associated yeasts. Traditionally, Tioconazole is used as a topical antifungal for curing PV. Previous investigations cited that human amniotic membrane (HAM), a placental tissue, has antimicrobial and anti-inflammatory activities and is useful as a dressing for healing skin lesions. Moreover, tea tree oil (TTO) has a potent antifungal efficacy. This clinical trial aims to achieve an alternative therapeutic treatment able to kill Malassezia and heal PV lesions using TTO-saturated HAM (TOSHAM), with little application times. This study subjected 120 patients with hypopigmented or hyperpigmented PV lesions; half patients were treated weekly with TOSHAM compared with the others who applying 1% Tioconazole cream daily as a traditional treatment. Microbiological evaluation of in vitro fungicidal activity of TOSHAM versus Tioconazole was carried out against Malassezia furfur culture. The clinical outcomes of this study proved the superior activity of TOSHAM to heal PV lesions than Tioconazole; this was in harmony with microbiological findings. This study approached a novel therapeutic treatment of PV with great outcomes by using TOSHAM.

Preliminary Assessment of the Mucosal Toxicity of Tea Tree (Melaleuca alternifolia) and Rosemary (Rosmarinus officinalis) Essential Oils on Novel Porcine Uterus Models

Antimicrobial resistance, an ever-growing global crisis, is strongly linked to the swine production industry. In previous studies, Melaleucaalternifolia and Rosmarinusofficinalis essential oils have been evaluated for toxicity on porcine spermatozoa and for antimicrobial capabilities in artificial insemination doses, with the future perspective of their use as antibiotic alternatives. The aim of the present research was to develop and validate in vitro and ex vivo models of porcine uterine mucosa for the evaluation of mucosal toxicity of essential oils. The in vitro model assessed the toxicity of a wider range of concentrations of both essential oils (from 0.2 to 500 mg/mL) on sections of uterine tissue, while the ex vivo model was achieved by filling the uterine horns. The damage induced by the oils was assessed by Evans Blue (EB) permeability assay and histologically. The expression of ZO-1, a protein involved in the composition of tight junctions, was assessed through immunohistochemical and immunofluorescence analysis. The results showed that low concentrations (0.2–0.4 mg/mL) of both essential oils, already identified as non-spermicidal but still antimicrobial, did not alter the structure and permeability of the swine uterine mucosa. Overall, these findings strengthen the hypothesis of a safe use of essential oils in inseminating doses of boar to replace antibiotics.

Essential oil-incorporated carbon nanotubes filters for bacterial removal and inactivation

In this study, essential oils (EO)-incorporated multi-walled carbon nanotubes (MWCNTs) filters were developed for achieving dual functions in effective removing bacteria from aqueous solutions and inactivating bacteria cells captured on the filters. Tea tree essential oil (TTO), lemon essential oil (LEO), and TTO-LEO-mixture were coated on MWCNTs filters with different MWCNTs loadings ranging from 3 mg to 6 mg. MWCNTs filters with 6.0 mg MWCNTs showed complete removal (100%) of E. coli cells from PBS buffer with 6.35 log10 decrease of cell numbers. TTO, LEO, and TTO/LEO Mix (1:1) coatings at the volume of 50 μL on MWCNTs filters achieved bacterial removal rates of >98%, and highly effective inactivation efficiency. TTO coatings had the highest antimicrobial efficacies than LEO and Mix coatings, MWCNTs filters with 50 μL TTO coating showed 100% inhibitory rate of the captured bacteria on the filter surfaces. Those captured but survived cells on filters with less TTO coating (20μL) significantly reduced their salt tolerances to 30 and 40 g/L NaCl in LB agar, and became less salt tolerance with longer incubation time on the filters. The developed TTO-MWCNTs filters had much higher antimicrobial efficacies than the filters with dual functions developed previously.

Melaleuca alternifolia essential oil abrogates hepatic oxidative damage in silver catfish (Rhamdia quelen) fed with an aflatoxin-contaminated diet

Mycotoxins are secondary metabolites produced by varieties of fungi that contaminate food and feed resources and are capable of inducing a wide range of toxicity. This problem is extensively aggravated due to the increasing replacement of fish meal by plant-derived proteins. Among the mycotoxins, aflatoxins have received a great deal of attention owing to their great prevalence in plant feedstuffs and to the detrimental effects on animals. The objective of this study was to evaluate whether dietary supplementation with tea tree (Melaleuca alternifolia) oil (TTO) would avoid or minimize the negative impacts on silver catfish (Rhamdia quelen) fed with aflatoxins-contaminated diets. Four treatments were tested: control (fish fed with a control diet); AFB (fish fed with a mycotoxin-contaminated diet - 1893 μg kg^-1 of AFB₁ and 52.2 μg kg^-1 AFB₂); TTO (fish fed with a control diet + 1 mL kg^-1 of TTO), and TTO + AFB (fish fed with a mycotoxin contaminated diet - 2324 μg kg^-1 of AFB₁ and 43.5 μg kg^-1 AFB₂ + 1 mL kg^-1 of TTO). Diets were tested in three replications and analyzed at days 5 and 10 of dietary intake. Significantly reduced antioxidant enzymes (SOD, GPx, and GST) and increased lipid peroxidation (LOOH) and protein carbonyl (PC) content in plasma and liver, with 16.6% mortality occurrence, were observed in the group fed aflatoxin-contaminated diet. Furthermore, aflatoxins also significantly increased plasmatic and hepatic ROS levels and decreased hepatic antioxidant capacity against peroxyl radical (ACAP) levels. Plasma cortisol levels were not altered by aflatoxicosis, but the intoxication induced hepatose. Notwithstanding, addition of TTO to the groups receiving aflatoxins showed a protective effect, avoiding the increase of ROS, LOOH, and PC levels in plasma and liver. Moreover, TTO treatment ameliorated the aflatoxin-associated liver damage. Thus, TTO supplementation at concentration of 1 mL kg^-1 in feed may be used in fish to increase antioxidant status and reduce the negative effects caused by aflatoxins toxicity.

Phenotype and RNA-seq-Based transcriptome profiling of Staphylococcus aureus biofilms in response to tea tree oil

Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that causes a wide range of diseases, including food poisoning. Tea tree oil (TTO), an essential oil distilled from Melaleuca alternifolia, is well-known for its antibacterial activities. TTO effectively inhibited all 19 tested strains of S. aureus biofilm and planktonic cells. Phenotype analyses of S. aureus biofilm cells exposed to TTO were performed by biofilm adhesion assays, eDNA detection and PIA release. RNA sequencing (RNA-seq) was used in our study to elucidate the mechanism of TTO as a potential antibacterial agent to evaluate differentially expressed genes (DEGs) and the functional network in S. aureus ATCC 29213 biofilms. TTO significantly changed (greater than a 2- or less than a 2-fold change) the expression of 304 genes in S. aureus contained in biofilms. The levels of genes related to the glycine, serine and threonine metabolism pathway, purine metabolism pathway, pyrimidine metabolism pathway and amino acid biosynthesis pathway were dramatically changed in the biofilm exposed to TTO. Furthermore, the expression changes identified by RNA-seq analysis were verified by real-time RT-PCR. To the best of our knowledge, this research is the first study to report the phenotype and expression profiles of S. aureus in biofilms exposed to TTO.

Treatment of scabies using a tea tree oil-based gel formulation in Australian Aboriginal children: protocol for a randomised controlled trial

INTRODUCTION

In remote Aboriginal communities in Australia, scabies affects 7 out of 10 children before their first birthday. This is more than six times the rate seen in the rest of the developed world. Scabies infestation is frequently complicated by bacterial infection, leading to the development of skin sores and other more serious consequences, such as septicaemia and chronic heart and kidney diseases. Tea tree oil (TTO) has been used as an antimicrobial agent for several decades with proven clinical efficacy. Preclinical investigations have demonstrated superior scabicidal properties of TTO compared with widely used scabicidal agents, such as permethrin 5% cream and ivermectin. However, current data are insufficient to warrant a broad recommendation for its use for the management of scabies because previous studies were small or limited to in vitro observations.

METHODS AND ANALYSIS

A pragmatic first trial will examine the clinical efficacy of a simple and low-cost TTO treatment against paediatric scabies and the prevention of associated secondary bacterial infections, with 1:1 randomisation of 200 participants (Aboriginal children, aged 5-16 years and living in remote Australia) into active control (permethrin 5% cream) and treatment (5% TTO gel) groups. The primary outcome for the study is clinical cure (complete resolution). Secondary outcome measures will include relief of symptoms, recurrence rate, adverse effects, adherence to treatment regimen and patient acceptability.

ETHICS AND DISSEMINATION

The project has received approvals from the University of Canberra Human Research Ethics Committee (HREC 16-133), Wurli-Wurlinjang Health Service Indigenous subcommittee and the Aboriginal Medical Services Alliance Northern Territory reference group. The results of this study will be published in core scientific publications, with extensive knowledge exchange activities with non-academic audiences throughout the duration of the project.

TRIAL REGISTRATION

ACTRN12617000902392; Pre-results.

Involvement of xanthine oxidase inhibition with the antioxidant property of nanoencapsulated Melaleuca alternifolia essential oil in fish experimentally infected with Pseudomonas aeruginosa

Nanoencapsulated Melaleuca alternifolia essential oil (tea tree oil, TTO) is a natural alternative treatment, with 100% therapeutic efficacy in fish experimentally infected with Pseudomonas aeruginosa, and has also potent protective effects linked with antioxidant properties. However, the pathways responsible for the antioxidant capacity remain unknown. Thus, this study evaluated whether the inhibition of seric xanthine oxidase (XO) activity can be considered a pathway involved in the antioxidant capacity of nanoencapsulated TTO in fish experimentally infected with P. aeruginosa. Seric samples from fish infected with P. aeruginosa showed increased XO activity, as well as increased uric acid and reactive oxygen species (ROS) levels. In contrast, the prophylactic treatment with nanoencapsulated TTO prevented these infection-induced alterations. Based on the evidence obtained, the upregulation of seric XO activity induced pro-oxidative effects in the serum of fish experimentally infected with P. aeruginosa, due to excessive formation of uric acid, which stimulates the release of ROS. This treatment was able to prevent the upregulated seric XO activity and, consequently, the excessive formation of uric acid and ROS. In summary, inhibition of seric XO activity can be considered a pathway involved in the antioxidant capacity of nanoencapsulated TTO in fish experimentally infected with P. aeruginosa.

Melaleuca alternifolia essential oil enhances the non-specific immune system and prevents oxidative damage in Rhamdia quelen experimentally infected by Aeromonas hydrophila: Effects on cholinergic and purinergic systems in liver tissue

The aim of this study was to evaluate the effects of M. alternifolia essential oil used to treat silver catfish (Rhamdia quelen) experimentally infected by Aeromonas hydrophila on oxidative stress variables, and for the first time, on hepatic enzymes of the cholinergic and adenosinergic systems. For that, fish were divided into six groups (A-F), each containing seven animals. Groups A, B and C were composed of uninfected animals, while animals in groups D, E and F were intramuscularly inoculated with A. hydrophila. Groups B and E received a prophylactic bath with M. alternifolia essential oil (50 μL/L, diluted in ethanol) for seven days, while groups C and F were exposed to ethanol. After the prophylactic baths, groups D, E and F were inoculated with 100 μL of A. hydrophila solution (2.1 × 10⁹ colony-forming unit). Two days after inoculation, the animals were euthanized and liver samples were collected. Infected animals (the group D) showed increased TBARS and protein carbonylation levels, while CAT, AChE and ADA activities decreased compared to uninfected animals (the group A). The prophylactic treatment with M. alternifolia essential oil (the group E) prevented the alterations caused by A. hydrophila, but it did not change AChE activity. Thus, the prophylactic treatment prevents damage caused by lipids and proteins, as well as alterations of the adenosinergic system, demonstrating that the anti-inflammatory effect of TTO is mediated by the adenosinergic pathway. In addition, TTO prophylactic treatment might be considered an important approach to prevent the hepatic damage caused by A. hydrophila.

The Effect of Polyhexanide, Octenidine Dihydrochloride, and Tea Tree Oil as Topical Antiseptic Agents on In Vivo Microcirculation of the Human Skin: A Noninvasive Quantitative Analysis

BACKGROUND

Antiseptics are indispensable for wound management and should focus not only on the efficacy in reducing the bacterial burden but also on how much they interfere in wound healing. In this study, the authors analyzed the direct effect of topical antiseptic agents on the microcirculation of intact human skin.

METHODS

The perfusion dynamics were assessed before, and 10 minutes after, the volunteers' fingers of the right hand (n = 20) were immersed in the following solutions - octenidine dihydrochloride, polyhexanide, tea tree oil, and saline solution. The authors used the Oxygen to See (LEA Medizintechnik GmbH, Giessen, Germany) diagnostic device for noninvasive determination of oxygen supply in microcirculation of blood perfused tissues, which combines a laser light to determine blood flow, as well as white light to determine hemoglobin oxygenation and the relative amount of hemoglobin.

RESULTS

Tea tree oil (&#247;19.0%) (B. Braun Melsungen AG, Melsungen, Germany) and polyhexanide (&#247;12.4%) (Lavanid, Serag Wiessner GmbH, Naila, Germany) caused a significant increase in blood flow compared to the negative control (-25.6%). Octenidine (Octenisept, Schülke & Mayr GmbH, Norderstedt, Germany) showed a nonsignificant trend towards an increase in blood flow (&#247;7.2%). There were alterations in the values of hemoglobin oxygenation and the relative amount of hemoglobin, but these were not significant.

CONCLUSION

Perfusion is an important factor for wound healing. Therefore, it might be advantageous if antiseptic agents would increase blood flow. Tea tree oil and polyhexanide have a positive effect on skin blood flow and can therefore be used especially in critically perfused wounds, provided the adverse reactions and the antimicrobial efficacy are comparable.

Essential oils to control ichthyophthiriasis in pacu, Piaractus mesopotamicus (Holmberg): special emphasis on treatment with Melaleuca alternifolia

In vitro effect of the Melaleuca alternifolia, Lavandula angustifolia and Mentha piperita essential oils (EOs) against Ichthyophthirius multifiliis and in vivo effect of M. alternifolia for treating ichthyophthiriasis in one of the most important South American fish, Piaractus mesopotamicus (Holmberg), were evaluated. The in vitro test consisted of three EOs, each at concentrations of 57 μL L(-1) , 114 μL L (-1) , 227 μL L(-1) and 455 μL L (-1) , which were assessed once an hour for 4 h in microtitre plates (96 wells). The in vitro results demonstrated that all tested EOs showed a cytotoxic effect against I. multifiliis compared to control groups (P < 0.05). The in vivo treatment for white spot disease was performed in a bath for 2 h day(-1) for 5 days using the M. alternifolia EO (50 μL L (-1) ). In this study, 53.33% of the fish severely infected by I. multifiliis survived after the treatment with M. alternifolia (50 μL L (-1) ) and the parasitological analysis has shown an efficacy of nearly 100% in the skin and gills, while all the fish in the control group died. Furthermore, the potential positive effect of M. alternifolia EO against two emergent opportunistic bacteria in South America Edwardsiella tarda and Citrobacter freundii was discussed.

Hydrogels Containing Nanocapsules and Nanoemulsions of Tea Tree Oil Provide Antiedematogenic Effect and Improved Skin Wound Healing

In previous works, we developed nanocapsules and nanoemulsions containing the tea tree oil. The aim of this work was to prepare and characterize hydrogels containing these nanocarriers, and to evaluate their in vivo efficacy in protecting skin damage induced by UVB and cutaneous wound healing. Hydrogels were prepared using Carbopol Ultrez and their physicochemical characteristics were evaluated: macroscopic analysis, pH, spreadability and rheological properties. The in vivo antiedematogenic effect was evaluated by ear thickness measurement after UVB-irradiation. In order to evaluate healing action of hydrogels, we investigated the regression of the cutaneous lesion in rats. Hydrogels showed homogeneous aspect and pH values between 5.6-5.8 and a non-Newtonian behavior. The presence of nanocapsules and nanoemulsions in hydrogels did not change their spreadability profile. The inclusion of tea tree oil in the nanocapsules and nanoemulsions allowed reducing the edema induced by UVB exposure. Hydrogel containing nanocapsules presented a higher reduction of the wound area compared to the hydrogel containing nanoemulsions and hydrogel containing allantoin. This study shows the feasibility of obtained dermatological formulations containing the tea tree oil associated in nanostructured systems. These formulations represent a promising approach to topical treatment of inflammatory disorders and wound healing.

Insecticidal and repellent effects of tea tree and andiroba oils on flies associated with livestock

This study aimed to evaluate the insecticidal and repellent effects of tea tree, Melaleuca alternifolia (Myrtales: Myrtaceae), and andiroba, Carapa guianensis (Sapindales: Meliaceae), essential oils on two species of fly. For in vitro studies, free-living adult flies were captured and reared in the laboratory. To evaluate the insecticidal effects of the oils, adult flies of Haematobia irritans (L.) and Musca domestica L. (both: Diptera: Muscidae) were separated by species in test cages (n = 10 per group), and subsequently tested with oils at concentrations of 1.0% and 5.0% using a negative control to validate the test. Both oils showed insecticidal activity. Tea tree oil at a concentration of 5.0% was able to kill M. domestica with 100.0% efficacy after 12 h of exposure. However, the effectiveness of andiroba oil at a concentration of 5.0% was only 67.0%. The insecticidal efficacy (100.0%) of both oils against H. irritans was observed at both concentrations for up to 4 h. The repellency effects of the oils at concentrations of 5.0% were tested in vivo on Holstein cows naturally infested by H. irritans. Both oils demonstrated repellency at 24 h, when the numbers of flies on cows treated with tea tree and andiroba oil were 61.6% and 57.7%, respectively, lower than the number of flies on control animals. It is possible to conclude that these essential oils have insecticidal and repellent effects against the species of fly used in this study.

The effect of thyme and tea tree oils on morphology and metabolism of Candida albicans

Members of Candida species cause significant problems in medicine and in many industrial branches also. In order to prevent from Candida sp. development, essential oils are more and more frequently applied as natural, non-toxic, non-pollutive and biodegradable agents with a broad spectrum of antimicrobial activity. The aim of the research was to determine changes in morphology and metabolic properties of Candida albicans in the presence of thyme and tea tree oils. Changes of enzymatic activity of isolates were observed in the presence of both tested essential oils, and they were primarily associated with loss or decrease of activity of all enzymes detected for control. Furthermore, only for 3 out of 11 isolates additional activity of N-acetyl-β-glucosaminidase, α-mannosidase, α-fucosidase and trypsin was detected. Vivid changes in biochemical profiles were found after treatment with tea tree oil and they were related to loss of ability to assimilate D-xylose, D-sorbitol and D-trehalose. The main differences in morphology of isolates compared to the control strain concerned formation of pseudohyphae structures. Both examined essential oils caused changes in cell and colony morphology, as well as in the metabolism of Candida albicans. However, the extent of differences depends on the type and concentration of an essential oil. The most important finding is the broad spectrum of changes in yeast enzymatic profiles induced by thyme and tea tree oils. It can be supposed that these changes, together with loss of ability to assimilate saccharides could significantly impact Candida albicans pathogenicity.

In vitro inhibition of herpes simplex virus type 1 replication by Mentha suaveolens essential oil and its main component piperitenone oxide

Several essential oils exert in vitro activity against bacteria and viruses and, among these latter, herpes simplex virus type 1 (HSV-1) is known to develop resistance to commonly used antiviral agents. Thus, the effects of the essential oil derived from Mentha suaveolens (EOMS) and its active principle piperitenone oxide (PEO) were tested in in vitro experimental model of infection with HSV-1. The 50% inhibitory concentration (IC50) was determined at 5.1μg/ml and 1.4μg/ml for EOMS and PEO, respectively. Australian tea tree oil (TTO) was used as control, revealing an IC50 of 13.2μg/ml. Moreover, a synergistic action against HSV-1 was observed when each oil was added in combination with acyclovir. In order to find out the mechanism of action, EOMS, PEO and TTO were added to the cells at different times during the virus life-cycle. Results obtained by yield reduction assay indicated that the antiviral activity of both compounds was principally due to an effect after viral adsorption. Indeed, no reduction of virus yield was observed when cells were treated during viral adsorption or pre-treated before viral infection. In particular, PEO exerted a strong inhibitory effect by interfering with a late step of HSV-1 life-cycle. HSV-1 infection is known to induce a pro-oxidative state with depletion of the main intracellular antioxidant glutathione and this redox change in the cell is important for viral replication. Interestingly, the treatment with PEO corrected this deficit, thus suggesting that the compound could interfere with some redox-sensitive cellular pathways exploited for viral replication. Overall our data suggest that both EOMS and PEO could be considered good candidates for novel anti-HSV-1 strategies, and need further exploration to better characterize the targets underlying their inhibition.

Influence of tea tree oil (Melaleuca alternifolia) on the cattle tick Rhipicephalus microplus

The aim of this study was to verify the influence of tea tree oil (TTO) (Melaleuca alternifolia) tested in its pure and nanostructured (TTO nanoparticles) forms on the reproduction of female Rhipicephalus microplus. For our purpose, female ticks were collected from naturally infected animals and treated in vitro with TTO (1, 5, and 10 %) and TTO nanoparticles (0.075, 0.375, and 0.75 %). In order to validate the tests, they were performed in triplicate using positive (amitraz) and negative (untreated) controls. It was possible to observe that pure TTO (5 and 10 %) and TTO nanoparticles (0.375 and 0.75 %) showed 100 % reproductive inhibition on female ticks. Additionally, pure TTO (1 %) also showed an acaricide effect (70 %), similarly to the positive control (78.3 %). This is the first study demonstrating the activity of pure TTO and TTO nanoparticles on female ticks. Therefore, based on these results, we were able to show that both forms and all concentrations of M. alternifolia affected tick reproduction by inhibiting egg laying and hatching. We were also able to show that TTO nanoparticles potentiated the inhibitor effect of pure TTO on the reproduction of R. microplus.

Repellency of DEET, picaridin, and three essential oils to Triatoma rubida (Hemiptera: Reduviidae: Triatominae)

The kissing bug, Triatoma rubida (Uhler) is a common hematophagous bug in Tucson, AZ, and is responsible for causing severe allergic reactions in some bitten individuals. DEET, picaridin, tea tree oil, peppermint oil, and citronella oil were tested for repellency to T. rubida and its ability to probe and feed on a small restrained rat. No long range repellency was observed with any of the test materials. The lowest repellent concentrations observed were: 10% DEET, 7% picaridin; 30% tea tree oil, 3.3% peppermint oil, and 0.165% citronella oil. Only citronella oil was able to stop all probing and feeding by T. rubida. Citronella oil appears to be a promising potential repellent to prevent sleeping people from being bitten by kissing bugs.

Ocular surface discomfort and Demodex: effect of tea tree oil eyelid scrub in Demodex blepharitis

The purpose of this study was to evaluate the relation between ocular discomfort and ocular Demodex infestation, and therapeutic effects of tea tree oil (TTO) in Demodex blepharitis patients. Three hundred and thirty-five patients with ocular discomfort were evaluated for ocular Demodex infestation and subjective symptoms with ocular surface discomfort index (OSDI) score. Among them, Demodex-infested patients were randomized to receive either eyelid scrubbing with TTO (TTO group,106 patients) or without TTO (Control group, 54 patients) for 1 month. Demodex were found in 84% of patients with ocular discomfort. The number of Demodex was significantly correlated with age (P = 0.04) and OSDI score (P = 0.024). After eyelid scrub treatment, Demodex count was reduced from 4.0 ± 2.5 to 3.2 ± 2.3 in the TTO group (P = 0.004) and from 4.3 ± 2.7 to 4.2 ± 2.5 in the control group (P = 0.27). Also, OSDI score was reduced from 34.5 ± 10.7 to 24.1 ± 11.9 in the TTO group (P = 0.001) and from 35.3 ± 11.6 to 27.5 ± 12.8 in the control group (P = 0.04). In conclusion, Demodex number showed a significant positive correlation with age and subjective ocular discomfort. The tea tree oil eyelid scrub treatment is effective for eliminating ocular Demodex and improving subjective ocular symptoms.

Activity of tea tree oil and nerolidol alone or in combination against Pediculus capitis (head lice) and its eggs

Head lice infestation is an emerging social problem in undeveloped and developed countries. Because of louse resistance increasing, several long-used insecticidal compounds have lost their efficacy, and alternatives, such as essential oils, have been proposed to treat this parasitic infestation. The present study investigated the efficacy of two natural substances: tea tree (Melaleuca alternifolia) oil and nerolidol (3,7,11-trimethyl-1,6,10-dodecatrien-3-ol) against lice and its eggs. Products were used alone and in combination (ratio 1:1 and 1:2) from 8 % dilution. The in vitro effect of natural substances at different concentrations were evaluated against 69 head lice (adults and nymphs) and 187 louse eggs collected from school children in Chieti-Pescara (Central Italy) over a 6-month period. The lice mortality was evaluated for 24 h by a stereo light microscope. The ovicidal activity was monitored by microscopic inspections for 15 days. Tea tree oil was more effective than nerolidol against head lice with 100 % mortality at 30 min and 1 % concentration. On the contrary, nerolidol expressed a more pronounced ovicidal activity inducing the failure of 50 % of the eggs to hatch at 1 % concentration after 4 days; the same effect was achieved by using a twice concentration of tea tree oil. The association of the two substances both in ratios 1:1 and 1:2 combined efficaciously their insecticidal and ovicidal effect; in particular, the ratio 1:2 (tea tree oil 0.5 % plus nerolidol 1 %) acted producing both the death of all head lice at 30 min and the abortive effect of louse eggs after 5 days. These results offer new potential application of natural compounds and display a promising scenario in the treatment of pediculosis resistant cases. The development of novel pediculicides containing essential oils could be, in fact, an important tool to control the parasitic infestation.

Plant essential oils and mastitis disease: their potential inhibitory effects on pro-inflammatory cytokine production in response to bacteria related inflammation

This paper highlights the role of plant volatile organic compounds, found in essential oils, for the treatment of bacteria related inflammation. This report is focused on tea tree oil, particularly its main compound terpinen-4-ol. Analysis of the published literature shows that many essential oils have significant antibacterial, antifungal and anti-inflammatory effects. Some of their major components, such as terpinen-4-ol, act by inhibiting pro-inflammatory cytokine expression while stimulating production of anti-inflammatory cytokines. Such observations may be exploited to encourage biotherapy against mastitis. The use of synthetic antibiotics is being increasingly discouraged because their presence in dairy milk may have potential downstream effects on population health and the agri-food chain. In the context of inflammation and related mammalian responses, understanding the interplay between volatile organic compounds, especially terpinen-4-ol, and cytokines during bacteria related inflammation should clarify their mode of action to control mastitis.

In vitro activity of antimicrobial agents against Pseudomonas tolaasii, pathogen of cultivated button mushroom

In vitro antibacterial activity tests of seven biofungicides (Ekstrasol, Bisolbisan, Bisolbifit, Serenade, Sonata, Timorex, F-Stop) and two disinfectants (colloidal silver alone and in combination with hydrogen peroxide) against the Pseudomonas tolaasii strain (NS3B6) were carried out by the disc-diffusion, broth microdilution and broth macrodilution method. Biofungicides tested in this study did not exhibit any antimicrobial activity in neither one of the methods used. Disc diffusion method revealed high sensitivity of the tested P. tolaasii strain to Ecocute based on colloidal silver and hydrogen peroxide. Both microdilution and macrodilution methods identified the same MICs and MBCs of Ecocute (0.19 mg/L) for P. tolaasii strain. MICs and MBCs values of silver alone were much higher (10 mg/L) compared to silver in combination with hydrogen peroxide.

Evaluation of double-decker traps for emerald ash borer (Coleoptera: Buprestidae)

Improved detection tools are needed for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive forest insect from Asia that has killed millions of ash (Fraxinus spp.) trees in North America since its discovery in Michigan in 2002. We evaluated attraction of adult A. planipennis to artificial traps incorporating visual (e.g., height, color, silhouette) and olfactory cues (e.g., host volatiles) at field sites in Michigan. We developed a double-decker trap consisting of a 3-m-tall polyvinyl pipe with two purple prisms attached near the top. In 2006, we compared A. planipennis attraction to double-decker traps baited with various combinations of manuka oil (containing sesquiterpenes present in ash bark), a blend of four ash leaf volatiles (leaf blend), and a rough texture to simulate bark. Significantly more A. planipennis were captured per trap when traps without the rough texture were baited with the leaf blend and manuka oil lures than on traps with texture and manuka oil but no leaf blend. In 2007, we also tested single prism traps set 1.5 m above ground and tower traps, similar to double-decker traps but 6 m tall. Double-decker traps baited with the leaf blend and manuka oil, with or without the addition of ash leaf and bark extracts, captured significantly more A. planipennis than similarly baited single prism traps, tower traps, or unbaited double-decker traps. A baited double-decker trap captured A. planipennis at a field site that was not previously known to be infested, representing the first detection event using artificial traps and lures. In 2008, we compared purple or green double-decker traps, single prisms suspended 3-5 m above ground in the ash canopy (canopy traps), and large flat purple traps (billboard traps). Significantly more A. planipennis were captured in purple versus green traps, baited traps versus unbaited traps, and double-decker versus canopy traps, whereas billboard traps were intermediate. At sites with very low A. planipennis densities, more A. planipennis were captured on baited double-decker traps than on other traps and a higher percentage of the baited double-decker traps captured beetles than any other trap design. In all 3 yr, peak A. planipennis activity occurred during late June to mid-July, corresponding to 800-1200 growing degree-days base 10 degrees C (DD10). Nearly all (95%) beetles were captured by the end of July at approximately 1400 DD10.

MRSA colonisation (eradicating colonisation in people without active/invasive infection)

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) has a gene that makes it resistant to methicillin as well as to other beta-lactam antibiotics, including flucloxacillin, beta-lactam/beta-lactamase inhibitor combinations, cephalosporins, and carbapenems. MRSA can be part of the normal body flora (colonisation), especially in the nose, but it can cause infection. Until recently, MRSA has primarily been a problem associated with exposure to the healthcare system, especially in people with prolonged hospital admissions, with underlying disease, or after antibiotic use. In many countries worldwide, a preponderance of S aureus bloodstream isolates are resistant to methicillin.

METHODS AND OUTCOMES

We conducted a systematic review and aimed to answer the following clinical question: What are the effects of treatment for MRSA nasal or extra-nasal colonisation? We searched: Medline, Embase, The Cochrane Library, and other important databases up to January 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

RESULTS

We found 9 systematic reviews, RCTs, or observational studies that met our inclusion criteria.

CONCLUSIONS

In this systematic review we present information relating to the effectiveness and safety of the following interventions: antiseptic body washes, chlorhexidine-neomycin nasal cream, mupirocin nasal ointment, systemic antimicrobials, tea tree oil preparations, and other topical antimicrobials.

Antimicrobial activity of two essential oils

The aim of the study was to evaluate the antimicrobial activity of essential oils in vitro for possible application to reduce the content of microorganisms in the air of animal houses. The essential oils of Cymbopogon citrarus L. and Malaleuca alternifolia L. were screened against bacteria Staphylococcus aureus, Enterococcus faecium, Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis and yeast Candida albicans. The minimal inhibitory concentration of the active essential oils was tested using broth dilution assay. The essential oils concentrations ranged from 0.1-50.0%. The combined effects of essential oils were tested for Malaleuca alternifolia L. and Cymbopogon citrarus L. concentrations ranged from 0.005-50.0%. The oils showed a wide spectrum of antibacterial activity. Concentrations of 0.1-0.5% of Cymbopogon citrarus L. and Malaleuca alternifolia L. reduced total microorganisms count of Proteus mirabilis and Candida albicans. High antibacterial activity was also revealed for Cymbopogon citrarus L. with bactericidal concentrations of 0.8% for Escherichia coli, 5.0% for Enterococcus faecium, 5.0% for Pseudomonas aeruginosa and 8.0% for Staphylococcus aureus. Bactericidal concentrations of Malaleuca alternifolia L. were 5.0% for Pseudomonas aeruginosa and Enterococcus faecium, and 8.0% for Staphylococcus aureus. The essential oils of Cymbopogon citrarus and Malaleuca alternifolia may be a promising alternative of air disinfection in animal houses.

Essential oils as biopreservatives: different methods for the technological application in lettuce leaves

Investigations were carried out to assess the efficiency of 3 essential oils, clove, tea tree, and rosemary, as natural preservatives during the postharvest of lettuce leaves. The effect of different concentration (1 and 0.5 MIC) of plant essential oils applied in 3 forms (spray, immersion, and capsules) was studied on lettuce leaves. The evolution of different microbial populations was evaluated during refrigerated storage. The application forms of the biopreservatives were shown to be an important factor in determining the effectiveness of the essential oils. Clove and tea tree essential oils at 1 MIC and applied embedded in lactose capsules presented a significant inhibition on mesophilic, psicrotrophic, and coliforms populations, while rosemary in none of the 3 technological applications forms exerted inhibitory effect on all microbial populations evaluated. Essential oils (at 0.5 MIC) applied by spray, immersion, and embedded in lactose capsules exerted lower inhibitory effects, with respect to 1 MIC, on the different microbial populations present on lettuce leaves. At the end of the storage (7 d), lettuce samples treated with tea tree, clove, and rosemary (at 1 and 0.5 MIC) by spray were the only organoleptically acceptable. It is concluded that clove and tea tree essential oils can control different microbial population present in lettuce. Practical Application: The exploration of naturally occurring antimicrobials in food preservation receives increasing attention due to consumer awareness of natural food products. Biopreservatives are useful in extending the shelf life of foods, reducing or eliminating pathogenic bacteria and increasing overall quality of food products. The effectiveness of essential oil application in foods is the result of factor associations such as applications forms, concentration applied, the way of action, storage temperatures. The application methods (spray, immersion, and embedded in lactose capsules) and the concentration of essential oils have been shown to be important factors in determining the effectiveness of these biopreservatives. The oil concentrations required to produce a certain level of inhibition in actual foods could be questionable due to the organoleptic impact. However, these novel natural preservatives in combination with other factors in obstacle technologies are an alternative to control the pathogen growth minimizing undesirable changes in organoleptic characteristics.

Synergism and postantibiotic effect of tobramycin and Melaleuca alternifolia (tea tree) oil against Staphylococcus aureus and Escherichia coli

The application of antimicrobial combinations may address the rising resistance to established classes of both systemic and topical agents and their clinical relevance is related to the presence of a significant postantibiotic effect (PAE). We investigated the effectiveness in vitro of the association between tobramycin and tea tree oil (TTO) against Gram-positive and Gram-negative bacteria. The minimal inhibitory concentrations, the bacterial killing and the PAE of tobramycin and TTO were determined both singly and in combination against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213. A synergistic interaction was observed against both strains tested: the mean PAEs were 1.3 and 1.7h for tobramycin against E. coli and S. aureus respectively, 10.8h for tobramycin and TTO (0.05%) against E. coli, 10.4h and 17.4h against S. aureus for tobramycin and TTO (0.25 and 0.50%, respectively). Longer PASMEs were observed with S. aureus after TTO/tobramycin exposure. In vitro interactions can improve the antimicrobial effectiveness of the antibiotic and may contribute for the development of novel topical agents for the treatment of skin lesions including conjunctiva and respiratory infections by inhalation.

The inhibition of Candida species by selected essential oils and their synergism with amphotericin B

In this work we highlight a possible synergistic anti-Candida effect between Melaleuca alternifolia, Origanum vulgare and Pelargonium graveolens essential oils and the antifungal compound Amphotericin B. The antifungal activity was assessed using the agar dilution method in eleven Candida strains. The results obtained indicate the occurrence of a synergistic interaction between the essential oils under study and Amphotericin B. P. graveolens essential oil appeared to be the most effective, inhibiting all the Candida species evaluated by this study.