Concentrations Of Tea Tree Oil Research Articles

Exploring the antimicrobial efficacy of tea tree essential oil and chitosan against oral pathogens to overcome antimicrobial resistance

BackgroundConsidering that antimicrobial resistance among oral pathogens is a significant concern in dental practice, with broader implications for overall health due to the oral microbiota serving as a reservoir for antibiotic resistance genes (ARGs), research into natural products is crucial for addressing this issue. ObjectiveThis study aimed to evaluate tea tree oil (TTO) and chitosan (CH) performance against oral pathogens, including mixed-species biofilm, and its effects on bacteria growth, in addition to chemical characterization and cytotoxicity of TTO. MethodsTea Tree Oil and low molecular weight chitosan were used in this study. The chemical composition of TTO was analyzed using gas chromatography coupled with mass spectrometry (GC-MS). To evaluate TTO's antimicrobial properties, time-kill and cell viability assays were conducted. Additionally, minimum inhibitory concentration (MIC), minimum microbiocidal concentration (MMC), checkerboard, and biofilm assays were performed using TTO and CH alone and in combination. ResultsTTO chromatography peaks found consistent with the standard ISO4730:2017 and literature. TTO and CH exhibited inhibitory activity against all tested microorganisms. The predominantly microbiostatic activity of TTO is probably related to terpinen-4-ol associated with terpinene. The oil at MIC value was able to delay the log phase of Aggregatibacter actinomycetemcomitans growth. Fibroblasts (L929) viability remained above 70 % during 24 h for TTO concentrations ranging from 0.5 to 0.0625 mg/ml. TTO-CH combination showed a synergistic activity (FIC = 0.5) against A. actinomycetemcomitans and Streptococcus sanguinis, at a concentration of 0,25MIC for both species. The compounds at MIC concentration inhibited both monospecies and mixed-species biofilms studied bacteria to the same extent as the azithromycin control. ConclusionTTO and CH demonstrated efficacy in combating oral pathogens and TTO-CH combination offers a promising approach to confront microbial resistance in the oral environment.

Tea tree oil influence on human keratocytes growth and viability

Tea tree oil (TTO) is used in ophthalmology to maintain healthy eyelid skin and to combat parasitic eyelid infections. Keratocytes belong to the structure of the corneal stoma and enable to maintain corneal homeostasis. TTO that reaches the surface of the eye in too high concentration may disturb the functions of these cells. The aim of the study was to test what concentration of TTO is safe for corneal keratocytes in vitro without causing a toxic effect. A normal human keratocytes (HK) cell line was used in the study. Morphology was visualized by light and fluorescence microscopy, cytometric analysis of the cell cycle and cytometric and spectrophotometric viability evaluation were performed. The level of nitric oxide was tested by Griess spectrophotometric method. TTO concentrations exceeding 0.01% significantly reduced cell viability. The IC50 values were on average 0.057%. Increasing TTO concentrations stimulated HK cells to release NOx. The observed values did not exceed 1 μM. The lowest TTO concentration increased the number of HK cells in the G1 phase of the cell cycle. Increasing TTO concentrations (≥0.1%) increased the number of cells in late apoptosis. TTO at concentrations ranging from 0.1% to 0.5% significantly changed cell morphology. Fluorescence analyzes confirmed that TTO at concentrations ≥0.1% induced apoptotic cell death. TTO exerts strong effect on ocular keratocytes depending on applied concentration. Concentrations exceeding 0.1% have a toxic effect on keratocytes, which die mainly by apoptosis. The ocular surface should be protected from excessive exposure to TTO, which may damage corneal stroma cells.

Effect of tea tree oil on candida adherence and surface roughness of heat cure acrylic resin

Background: Denture cleansing was an important step that could prevent the spread of infection and improve a patient's health, the durability of the dentures, and the overall quality of life; therefore, it was necessary to choose a suitable cleanser that, in addition to being effective, did not have an unfavorable effect on the qualities of the denture base resin itself when used for an extended period. For this purpose, this study aimed to evaluate the effect of tea tree oil (TTO) on Candida albicans adhesion and the surface roughness property of poly(methyl methacrylate) denture material after immersion in TTO. Methods: A total of 55 heat-cured acrylic resin specimens were used for C. albicans adherence and surface roughness tests. They were distributed into groups (0.25%, 0.5%, 0.75%, and 1%) of TTO, distilled water (DW), and 2% clorhexidine digluconate, totaling five specimens for each group. The specimens were immersed in accordance with their group for 10 minutes. Surface roughness was determined by a profilometer, and C. albicans adherence was determined by measuring optical density with a spectrophotometer. For comparisons between groups for surface roughness and disinfection tests, one-way ANOVA was performed on SPSS program, considering α = 0.05. Results: TTO had a statistically significant effect on C. albicans adhesion to heat-cured acrylic resin (P < 0.05) compared with negative control. Meanwhile, no statistically significant difference was found between 0.75% and 1% TTO concentrations (P > 0.05), whereas the surface roughness test showed a statistically non-significant difference between TTO concentrations and DW (P > 0.05). Conclusions: Immersion of acrylic resin in TTO was effective in decreasing C. albicans adhesion to it, and the greatest decrease was obtained by 1% TTO. The surface roughness test showed a non-significant difference in acrylic roughness after immersion in TTO.

Comparison of tea tree oil 5%, tea tree oil 10%, and nystatin inhibition zones against vaginal Candida isolates in pregnancy.

Vulvovaginal candidiasis (VVC) in pregnancy frequently develops into recurrent infections. Clinical study suggests that conventional topical treatments for VVC are not always enough to eradicate Candida spp. from the vaginal microenvironment. This study aimed to evaluate the antifungal activity of tea tree oil (TTO) 5% and TTO 10% against Candida species causing VVC in pregnancy. In vitro experimental study was conducted in the Mycology Laboratory at Dermatovenereology Outpatient Clinic Dr. Soetomo General Hospital Surabaya. Eighteen isolates of Candida species were isolated from the vaginal thrush of 15 pregnant women diagnosed with VVC from March to May 2021. Antifungal susceptibility of TTO 5% and TTO 10% was evaluated by the disc diffusion method, with the inhibitory zone diameter as the main outcome. The mean inhibitory zone diameter of TTO 5%, TTO 10%, and nystatin against all Candida spp. was 7.26 mm, 8.64 mm, and 25.57 mm, respectively (p < 0.001). The mean inhibitory zone diameter of TTO 5%, TTO 10%, and nystatin tend to be larger in C. albicans compared to the non-albicans, but the difference is not significant. Nystatin displayed the largest mean inhibitory zone diameters compared to TTO 5% and TTO 10% (p < 0.001) in all Candida species. Increased concentration from TTO 5% to TTO 10% resulted in a slight increment in the mean inhibitory zone diameters in all-Candida species (p = 0.001). Tea Tree Oil displayed antifungal activity against Candida species causing VVC in pregnancy. Further studies are required to investigate optimal TTO concentrations as a VVC treatment in pregnancy.

Effect of tea tree oil addition on the microstructure, structure and selected properties of chitosan-based coatings electrophoretically deposited on zirconium alloy substrates

In this work, Tea Tree Oil (TTO)/chitosan coatings of different TTO concentrations were electrophoretically deposited (EPD) on Zr-2.5Nb alloy substrates. The properties of solutions and EPD kinetics of TTO/chitosan coatings and pure chitosan coatings used as a reference material were analysed. The incorporation of TTO into chitosan solutions changed their zeta potential and conductivity, as well as influencing the EPD kinetics. The microstructure of the coatings consisted of TTO droplets embedded into the chitosan matrix. The addition of TTO resulted in the formation of new hydrogen bonds between chitosan and the TTO main components. Both pure chitosan and TTO/chitosan coatings deposited from solutions containing up to 10 mL/L TTO had excellent adhesion to the rough substrates. The mechanical interlocking was indicated as the main adhesion mechanism of coatings. However, chemical bonding was not excluded. The coatings exhibited a hydrophobic character and showed about 50% lower SFE with a very low value of the polar component compared to substrates. The obtained results on EPD and the characterisation of microstructure, structure and selected properties show that chitosan coatings containing TTO are promising as antimicrobial coatings for metallic biomaterial substrates. However, the antimicrobial properties and cytotoxicity of coatings should be further investigated.

The comparative in vitro killing activity of tea tree oil versus permethrin on Demodex folliculorum of rosacea patients.

Demodex mites have been implicated in several cutaneous disorders compelling the research efforts for effective anti-Demodex therapy. Compare the survival time (ST) of Demodex folliculorum exposed to six different concentrations of tea tree oil (TTO) versus a positive control (permethrin 5%) and a negative control (immersion oil) group. The wastes of rosacea patients' standardized superficial skin biopsy samples were recruited for the trial. The primary outcome measure of this study was the survival time, defined as the period between the exposure of study agents to the complete cessation of Demodex movements. All differences between the mean survival times of 2.5% (54.0±6.1), 5% (39.0±3.9), 10% (22.0±2.5), 25% (13.0±2.5), 50% (7.8±0.6), and 100% TTO (3.3±1.3) were significant (p<0.05). The ST of the negative control group was 196.0±23.6min. The ST of permethrin 5% was 12.5±1.9 that did not show a statistically significant difference from the ST of TTO 25% (p=0.628). The survival times of the six different TTO groups confirmed a dose-related pattern, all of which had survival times shorter than the negative control (immersion oil). TTO 25% had comparable efficacy to the positive control agent (permethrin 5%).

Tea tree oil for Demodex blepharitis.

Demodex blepharitis is a chronic condition commonly associated with recalcitrant dry eye symptoms though many people with Demodex mites are asymptomatic. The primary cause of this condition in humans is two types of Demodex mites: Demodex folliculorum and Demodex brevis. There are varying reports of the prevalence of Demodex blepharitis among adults, and it affects both men and women equally. While Demodex mites are commonly treated with tea tree oil, the effectiveness of tea tree oil for treating Demodex blepharitis is not well documented. To evaluate the effects of tea tree oil on ocular Demodex infestation in people with Demodex blepharitis. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 6); Ovid MEDLINE; Embase.com; PubMed; LILACS; ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We used no date or language restrictions in the electronic search for trials. We last searched the databases on 18 June 2019. We included randomized controlled trials (RCTs) that compared treatment with tea tree oil (or its components) versus another treatment or no treatment for people with Demodex blepharitis. Two review authors independently screened the titles and abstracts and then full text of records to determine their eligibility. The review authors independently extracted data and assessed risk of bias using Covidence. A third review author resolved any conflicts at all stages. We included six RCTs (1124 eyes of 562 participants; 17 to 281 participants per study) from the US, Korea, China, Australia, Ireland, and Turkey. The RCTs compared some formulation of tea tree oil to another treatment or no treatment. Included participants were both men and women, ranging from 39 to 55 years of age. All RCTs were assessed at unclear or high risk of bias in one or more domains. We also identified two RCTs that are ongoing or awaiting publications. Data from three RCTs that reported a short-term mean change in the number of Demodex mites per eight eyelashes contributed to a meta-analysis. We are uncertain about the mean reduction for the groups that received the tea tree oil intervention (mean difference [MD] 0.70, 95% confidence interval [CI] 0.24 to 1.16) at four to six weeks as compared to other interventions. Only one RCT reported data for long-term changes, which found that the group that received intense pulse light as the treatment had complete eradication of Demodex mites at three months. We graded the certainty of the evidence for this outcome as very low. Three RCTs reported no evidence of a difference for participant reported symptoms measured on the Ocular Surface Disease Index (OSDI) between the tea tree oil group and the group receiving other forms of intervention. Mean differences in these studies ranged from -10.54 (95% CI - 24.19, 3.11) to 3.40 (95% CI -0.70 7.50). We did not conduct a meta-analysis for this outcome given substantial statistical heterogeneity and graded the certainty of the evidence as low. One RCT provided information concerning visual acuity but did not provide sufficient data for between-group comparisons. The authors noted that mean habitual LogMAR visual acuity for all study participants improved post-treatment (mean LogMAR 1.16, standard deviation 0.26 at 4 weeks). We graded the certainty of evidence for this outcome as low. No RCTs provided data on mean change in number of cylindrical dandruff or the proportion of participants experiencing conjunctival injection or experiencing meibomian gland dysfunction. Three RCTs provided information on adverse events. One reported no adverse events. The other two described a total of six participants randomized to treatment with tea tree oil who experienced ocular irritation or discomfort that resolved with re-educating the patient on application techniques and continuing use of the tea tree oil. We graded the certainty of the evidence for this outcome as very low. The current review suggests that there is uncertainty related to the effectiveness of 5% to 50% tea tree oil for the short-term treatment of Demodex blepharitis; however, if used, lower concentrations may be preferable in the eye care arena to avoid induced ocular irritation. Future studies should be better controlled, assess outcomes at long term (e.g. 10 to 12 weeks or beyond), account for patient compliance, and study the effects of different tea tree oil concentrations.

English

Tea Tree oil (TTO), the essential oil from the Australian native Melaleuca alternifolia has demonstrated a variety of beneficial efficacies including antimicrobial, antifungal, antiviral and anti-inflammatory. This report discusses data obtained on the in vitro activity of TTO on human glioblastoma cells U87MG. Cell viability was examined by 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide MTT assay. Growth was investigated by incubating cells with various concentrations of TTO (0.025 and 0.05 %) for 24, 48 or 72 h and daily cell count. Cell cycle and apoptosis assay were assessed by flow citometry. TTO decreased cell viability in a dose and time-dependent manner. . The cell cycle distribution showed that TTO enhanced the accumulation of the cells in G0/G1 phase. The analysis by Western blot of protein related to cell cycle (CDK2 and p27), cell apoptosis (caspase 6 and 8), necrosis (TNFR1 and RIP1) demonstrated that TTO induces U87MG growth inhibition by more synergic mechanisms: necrosis, low level apoptosis and cell cycle arrest. TTO induces also in vivo glioblastoma tumor growth inhibition in a murine subcutaneous model. Key words: Brain cancer, tea tree oil, terpinol, glioblastoma, natural drug, adjuvant chemotherapy, temozolomide, apoptosis, cell cycle. &nbsp; &nbsp;

Synergistic effect of tea tree oil on fungi causing vaginal thrush in pregnant women

Background: Vulvovaginal candidiasis(VVC), or Vaginal thrush, is a vaginitis caused by the overgrowth of some opportunistic yeasts of the genus Candida spp. Australian Tea Tree Oil (TTO) is one of the most important essential oils that contain many compounds that are effective against many bacteria and fungi, which may match the effect of common antibiotics.&#x0D; Objective: The aim of this study was to isolate and diagnose fungi that causing vaginal thrush, in pregnant women and to study the effect of (pregnancy and pregnancy sequence and age) on the rate of infection compared to non-pregnant, as well as to study the drug sensitivity of isolates towards a number of antifungal and compared that with the inhibitory effectiveness of tea tree oil.&#x0D; Material and Methods: 75 vaginal swabs from pregnant women and 50 from non-pregnant women were collected at ages ranging from 17-65 years. The isolates were diagnosed using several methods, including the Vitek2 Compact system. 17 isolates were selected to study the inhibitory effect of ten antifungal agents, six of them were automatically tested by the Vitek 2 compact system, which contains a sensitivity test kit (AST-YS07 Card). The essential oil (TTO) was analyzed by GC-MS to detect its content of active compounds. The inhibitory effect of TTO was studied according to "Broth dilution" method to determine minimum inhibitory concentration (MIC) for it, the inhibitory effect of four concentrations of TTO (100%, 50%, 25%, 12.5 %) was also tested according to "well diffusion" method. This investigation also included a study of the mechanism of action (TTO).&#x0D; RESULTS: The rate of infection among pregnant women was (41%) with the highest rate of infection during the third trimester of pregnancy, while the percentage of non-pregnant women was only 8%. Vaginal infection was also prevalent in the age group ranged between (17-29 years).The isolates showed resistance to (Ketoconazol, Terbinafine) while they were sensitive to (Nystatin, clotrimazol), as well as sensitive to all antifungal of (AST-YS07 Card). The analysis of the TTO using chromatogram showed that it contains 32 chemical compounds, most of them are monoterpene like (Terpinen-4-ol, 1, 8-Cineol). The MIC of TTO ranged between (4 - &lt; 2 µl/ ml). The function of TTO is to destroy the structural structure of the cell membrane and change its permeability, thereby leakage of cellular components and cell death. &#x0D; Conclusion: Pregnancy increases the rate of vaginal candidiasis in women, especially during the third trimester. TTO is highly effective in inhibiting the growth of opportunistic candida yeasts.&#x0D; &#x0D;

Tea tree oil exposure in cats and dogs

Tea tree oil is an essential oil from the Australian tea tree Melaleuca alternifolia and is sometimes promoted as a natural or herbal treatment for fleas in pets. Although products containing low concentrations of tea tree oil are not expected to be a problem in pets, the use of pure tea tree oil directly on the skin is potentially very serious in pets and should never be used. Exposure may cause ataxia, salivation, lethargy, coma and tremor. Dermal exposure to tea tree oil may also result in dermatitis as the oil is irritant to skin. Even a few drops of pure tea tree oil applied dermally can cause clinical signs, and deaths have occurred in pets treated with pure tea tree oil. Treatment includes dermal decontamination and supportive care.

Tea tree oil presents in vitro antitumor activity on breast cancer cells without cytotoxic effects on fibroblasts and on peripheral blood mononuclear cells

The purpose of this study was to investigate some possible mechanisms underlying the in vitro antitumor activity of tea tree oil (TTO) on human and mouse breast cancer cells (MCF-7 and 4T1, respectively) and its cytotoxicity on fibroblasts (HFF-1) and on peripheral blood mononuclear cells (PBMCs). TTO High-Resolution Gas Chromatography (HRGC) showed seventeen main constituents, such as Terpinen-4-ol, γ-Terpinene, and α-Terpinene. High TTO concentrations (≥ 600 μg/mL) showed a remarkable antitumor activity, decreasing cell viability and cell proliferation of MCF-7 and 4T1 cells. TTO at 300 μg/mL increased the number of MCF-7 cells in the early stages of apoptosis and increased the BAX/BCL-2 genes ratio. TTO, mainly at 300 μg/mL, decreased cell growth and arrested MCF-7 cells in the S phase of the cell cycle. Lower antitumor concentrations (≤300 μg/mL) evaluated in MCF-7 and 4T1 cells were not cytotoxic to PBMCs and HFF-1. Also, TTO (300 μg/mL) was able to induce cell proliferation in fibroblasts after 72 h, indicating non-cytotoxic effect in these cells. TTO exhibited in vitro antitumor effect on MCF-7 and 4T1 cells by decreasing cell viability and modulating apoptotic pathways and cell cycle arrestment of MCF-7 cells. In this sense, our study provides new perspectives on the potential use of TTO for the development of new alternative therapies to treat topically locally advanced breast cancer (LABC).

STUDIES ON THE FORMULATION, PHYSICAL STABILITY, AND IN VITRO ANTIBACTERIAL ACTIVITY OF TEA TREE OIL (MELALEUCA ALTERNIFOLIA) NANOEMULSION GEL

Objective: This study aimed to formulate tea tree oil into a nanoemulsion gel dosage form and evaluate its physical stability and antibacterial activity.Methods: Nanoemulsion gels were formulated with various concentrations of tea tree oil, namely, 5%, 7%, and 9%, using Tween-80 as a surfactantand propylene glycol as a cosurfactant. The tea tree oil nanoemulsion gels showed a stable physical appearance over 8 weeks of storage at lowtemperature (4±2°C) and room temperature (25±2°C), cycling test, and centrifugation test.Results: The best formula was nanoemulsion gel formulation 1 (F1), which contained 5% tea tree oil, due to its good stability, smaller globule size,and greater viscosity. The results for antibacterial activity, determined by in vitro study, showed that the tea tree oil nanoemulsion gels exhibitedantibacterial activity against Propionibacterium acnes through the formation of an inhibition zone.Conclusion: Higher concentrations of tea tree oil in nanoemulsion gels (5%, 7%, and 9%) showed greater mean inhibition zones (28.33±0.88 mm,30.33±0.33 mm, and 31.67±0.33 mm, respectively).

Tea tree oil exhibits antifungal activity against Botrytis cinerea by affecting mitochondria

In order to investigate the effects of tea tree oil (TTO) on mitochondrial morphology and function in Botrytis cinerea, mycelia were treated with TTO at different concentrations. TTO at 2ml/l severely damaged mitochondria, resulting in matrix loss and increased mitochondrial irregularity. Mitochondrial membrane permeability was increased by TTO, as evidenced by a decrease in intracellular adenosine triphosphate (ATP) content and an increase in extracellular ATP content. Increasing concentrations of TTO decreased the activities of enzymes related to mitochondrial function and the tricarboxylic acid (TCA) cycle, affecting malic dehydrogenase, succinate dehydrogenase, ATPase, citrate synthetase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, while sharply increasing the level of reactive oxygen species (ROS). These results suggest that mitochondrial damage, resulting in the disruption of the TCA cycle and accumulation of ROS, is involved in the mechanism of TTO antifungal activity against B. cinerea.

Inhibition effect of tea tree oil on Listeria monocytogenes growth and exotoxin proteins listeriolysin O and p60 secretion.

This is the first report on the influence of subinhibitory concentrations of tea tree oil (TTO) on the secretion of listeriolysin O (LLO) and p60, the critical virulence factors involved in Listeria pathogenesis. The results showed that TTO at 0·25mgml-1 reduced the secretion of LLO and p60 to 10 and 34·9% respectively, in addtion, the transcription of hly and iap was reduced to 10 and 4·3% at 0·5mgml-1 respectively. We propose that TTO could be used as a promising antimicrobial compound and virulence inhibitor against L.monocytogenes.

The dynamics and mechanism of the antimicrobial activity of tea tree oil against bacteria and fungi.

Tea tree oil (TTO) is a yellow liquid extracted from Melaleuca alternifolia. Although the antimicrobial activity of TTO has been known for a long time, its specific antimicrobial effects and mechanism underlying these remain poorly characterized. The present study investigated the chemical composition of TTO and the dynamics and mechanism of its antimicrobial activities in two bacterial and two fungal strains. Gas chromatography-mass spectrometry analysis identified alkenes and alcohols as the main constituents of TTO. Terpinen-4-ol was the most abundant individual component, accounting for approximately 23% of the TTO. Poisoned food technique assessment showed that the minimum inhibitory concentrations of TTO for bacterial strains (Escherichia coli and Staphylococcus aureus) and fungal strains (Candida albicans and Aspergillus niger) were 1.08 and 2.17mg/mL, respectively. Antimicrobial dynamic curves showed that with increasing concentrations of TTO, the rate of cell killing and the duration of growth lag phase increased correspondingly. These data indicated that TTO produced concentration and time-dependent antimicrobial effects. The minimum bactericidal and fungicidal concentrations of TTO were 2.17, 4.34, and 4.34 against E. coli, S. aureus, and C. albicans, respectively. However, A. niger conidia were not completely eradicated, even after 3days in the presence of 17.34mg/mL TTO. Transmission electron microscopy images indicated that TTO penetrated the cell wall and cytoplasmic membrane of all the tested bacterial and fungal strains. TTO may also penetrate fungal organelle membrane. These findings indicated that TTO maybe exerts its antimicrobial effects by compromising the cell membrane, resulting in loss of the cytoplasm and organelle damage, which ultimate leads to cell death.

On the formation, physicochemical properties and antibacterial activity of colloidal systems containing tea tree (Melaleuca alternifolia) oil

Abstract In this study, we investigated the influence of tea tree oil (TTO) on the formation and physicochemical properties of colloidal systems stabilized by the nonionic surfactant polysorbate 80. These systems were prepared by spontaneous emulsification with quantities of TTO ranging from 0% to 0.5% w/w, at a fixed surfactant concentration (2% w/w). The dispersed structures usually found in microemulsions (oil-swollen micelles) and emulsions (oil droplets) were produced under these experimental conditions. The relative contribution of the oil-swollen micelles (∼11 nm) to the overall scattered intensity decreased as a function of TTO concentrations, while an opposite behavior was observed for the oil droplets (∼275 nm). Such variations led to significant increases in the z-average particle size and turbidity of the TTO containing samples. Additional investigations also revealed that the surface charge and fluidity of oil-swollen micelles and oil-droplets are very similar. Although their sizes remained practically unchanged over the storage time, the oil droplets were considered to be physically unstable since they undergo a gradual transition to oil-swollen micelles. Finally, in vitro susceptibility studies with TTO containing colloidal systems showed that the encapsulation of this essential oil with polysorbate 80 did not improve its antimicrobial activity. This effect has been attributed to the electrostatic repulsion between the dispersed structures and the bacterial outer membrane as well as a greater tendency of essential oil molecules to remain dissolved in the hydrophobic core of colloidal systems.

Effect of tea tree oil on Staphylococcus aureus growth and enterotoxin production

Staphylococcus aureus (S. aureus), a major food-borne pathogen, causes disease in mammalian hosts by producing a wide variety of exoproteins, such as α-hemolysin and staphylococcal enterotoxins. Tea tree oil (TTO), an essential oil, has broad-spectrum antimicrobial activity. The objectives of this study were to evaluate the inhibitory effects of TTO on S. aureus growth and on α-hemolysin, enterotoxins A and B production. In this study, the effect of TTO on S. aureus growth in laboratory medium and pasteurized milk was determined by time-kill assays. Treatment with half of minimal inhibitory concentration (MIC) of TTO demonstrated very little or no reduction in numbers of viable ATCC 29213 cells; however, 1 × MIC of TTO reduced the viable cell count more noticeably, and 2 × MIC of TTO demonstrated an even greater reduction in the viable cell count, both in TSB and milk. The influence of TTO on enterotoxins was determined by real-time reverse transcriptase-PCR (real-time RT-PCR), a hemolysis assay, Western blot and a tumor necrosis factor alpha (TNF-α) assay. The real-time RT-PCR results revealed that the transcription of genes encoding α-hemolysin, staphylococcal enterotoxin A (SEA) and staphylococcal enterotoxin B (SEB) were down regulated after S. aureus was exposed to TTO (0.0625 mg/mL-0.5 mg/mL). The hemolytic assay showed that S. aureus hemolytic activity was inhibited by subinhibitory concentrations of TTO (0.0625 mg/mL-0.5 mg/mL). The Western blot assay identified that the production of the three virulence factors was inhibited by TTO (0.0625 mg/mL-0.5 mg/mL). Moreover, the enzyme linked immunosorbent assay (ELISA) demonstrated that TNF-α production was suppressed by TTO treatment in RAW264.7 cells stimulated by S. aureus supernatant containing staphylococcal enterotoxins (SEs).

In vitro activity of Melaleuca alternifolia (tea tree) oil on filamentous fungi and toxicity to human cells.

Invasive fungal wound infections (IFIs) are increasingly reported in trauma patients and cause considerable morbidity and mortality despite standard of care treatment in trauma centers by experienced medical personnel. Topical agents such as oil of melaleuca, also known as tea tree oil (TTO), have been proposed for adjunctive treatment of IFIs. We evaluated the activity of TTO against filamentous fungi associated with IFIs by testing 13 clinical isolates representing nine species via time-kill assay with seven concentrations of TTO (100%, 75%, 50%, 25%, 10%, 5%, and 1%). To ascertain the safety of topical application to wounds, cell viability assays were performed in vitro using human fibroblasts, keratinocytes, osteoblasts, and umbilical vein endothelial cells with 10 concentrations of TTO (75%, 50%, 25%, 10%, 5%, and 10-fold serial dilutions from 1 to 0.0001%) at five time points (5, 15, 30, 60, and 180 min). Compatibility of TTO with explanted porcine tissues was also assessed with eight concentrations of TTO (100%, 75%, 50%, 25%, 10%, 5%, 1%, and 0.1%) at the time points used for cellular assays and at 24 h. The time-kill studies showed that fungicidal activity was variable between isolates. The effect of TTO on cell viability was primarily concentration dependent with significant cytotoxicity at concentrations of ≥ 10% and ≥ 50% for cells lines and whole tissue, respectively. Our findings demonstrate that TTO possesses antifungal activity against filamentous fungi associated with IFIs; furthermore that negligible effects on whole tissues, in contrast to individual cells, were observed following exposure to TTO. Collectively, these findings indicate a potential use of TTO as topical treatment of IFIs.

The influence of tea tree oil (Melaleuca alternifolia) on fluconazole activity against fluconazole-resistant Candida albicans strains.

The aim of this study was to evaluate the activity of fluconazole against 32 clinical strains of fluconazole-resistant Candida albicans, and C. albicans ATCC 10231 reference strain, after their exposure to sublethal concentrations of tea tree oil (TTO) or its main bioactive component terpinen-4-ol. For all tested fluconazole-resistant C. albicans strains TTO and terpinen-4-ol minimal inhibitory concentrations (MICs) were low, ranging from 0.06% to 0.5%. The 24-hour exposure of fluconazole-resistant C. albicans strains to fluconazole with sublethal dose of TTO enhanced fluconazole activity against these strains. Overall, 62.5% of isolates were classified as susceptible, 25.0% exhibited intermediate susceptibility, and 12.5% were resistant. For all of the tested clinical strains the fluconazole MIC decreased from an average of 244.0 μg/mL to an average of 38.46 μg/mL, and the fluconazole minimal fungicidal concentrations (MFC) decreased from an average of 254.67 μg/mL to an average of 66.62 μg/mL. Terpinen-4-ol was found to be more active than TTO, and strongly enhanced fluconazole activity against fluconazole-resistant C. albicans strains. The results of this study demonstrate that combining natural substances such as TTO and conventional drug such as fluconazole, may help treat difficult yeast infections.

Microbiological studies of the cream for use in the diabetic foot syndrome

Microbiological stability is an important requirement to the medicines developed. In order to prevent microbial contamination of medicines it is necessary to use effective antimicrobial preservatives or active substances with a high preservative effect. Tea tree oil (Melaleuca alternifolia Maid) is a promising antimicrobial substance in development of drugs for use in the diabetic foot syndrom. The microbiological study of the cream with α-lipoic acid, urea, and tea tree oil developed for use in the diabetic foot syndrome has been carried out. The study of the preservative action efficiency of tea tree oil was conducted according to the method of the SPhU. The criterion for efficiency evaluation of the preservative action of the samples under research was decrease of the number of viable cells of microorganisms in the medicines for the certain periods of time after inoculation. The data obtained have shown that the test samples with different concentrations of tea tree oil provide the antimicrobial effect in relation to all test strains of the microorganisms used. The number of microorganisms decreased during storage. It has been found that introduction of tea tree essential oil in the concentration of 3% provides microbiological stability of the medicine developed according to the requirements of the SPhU. By efficiency of its preservative action the essential oil of tea tree meets the requirements of criterion “A” according to the SPhU, and it allows not to add extra preservatives to the cream developed.