Design and Evaluation of Microemulsion-Based Drug Delivery Systems for Biofilm-Based Infection in Burns.

Normal skin is the first line of defense in the human body. A burn injury makes the skin susceptible to bacterial infection, thereby delaying wound healing and ultimately leading to sepsis. The chances of biofilm formation are high in burn wounds due to the presence of avascular necrotic tissue. The most common pathogen to cause burn infection and biofilm is Pseudomonas aeruginosa. The purpose of this study was to create a microemulsion (ME) formulation for topical application to treat bacterial burn infection. In the present study, tea tree oil was used as the oil phase, Tween 80 and transcutol were used as surfactants, and water served as the aqueous phase. Pseudo ternary phase diagrams were used to determine the design space. The ranges of components as suggested by the design were chosen, optimization of the microemulsion was performed, and in vitro drug release was assessed. Based on the characterization studies performed, it was found that the microemulsion were formulated properly, and the particle size obtained was within the desired microemulsion range of 10 to 300 nm. The I release study showed that the microemulsion followed an immediate release profile. The formulation was further tested based on its ability to inhibit biofilm formation and bacterial growth. The prepared microemulsion was capable of inhibiting biofilm formation.

Unraveling the effective inhibition of α-terpinol and terpene-4-ol against Aspergillus carbonarius: Antifungal mechanism, ochratoxin A biosynthesis inhibition and degradation perspectives.

Aspergillus carbonarius, a common food-contaminating fungus, produces ochratoxin A (OTA) and poses a risk to human health. This study aimed to assess the inhibitory activity of tea tree essential oil and its main components, Terpene-4-ol (T4), α-terpineol (αS), and 3-carene (3C) against A. carbonarius. The study showed αS and T4 were the main antifungal components of tea tree essential oil, which primarily inhibit A. carbonarius growth through cell membrane disruption, reducing antioxidant enzyme activities (catalase, peroxidase, superoxide dismutase) and interrupting the tricarboxylic acid cycle. Furthermore, αS and T4 interacted with enzymes related to OTA biosynthesis. Molecular docking and molecular dynamics show that they bound mainly to P450 with a minimum binding energy of -7.232 kcal/mol, we infered that blocking the synthesis of OTA precursor OTß. Our hypothesis was preliminarily verified by the detection of key substances in the OTA synthesis pathway. The results of UHPLC-QTOF-MS2 analysis demonstrated that T4 achieved a degradation rate of 43 % for OTA, while αS reached 29.6 %, resulting in final breakdown products such as OTα and phenylalanine. These results indicated that α-terpinol and Terpene-4-ol have the potential to be used as naturally safe and efficient preservatives or active packaging to prevent OTA contamination.

Melaleuca alternifolia essential oil in a natural product-based formulation: Antimicrobial and healing effects in Staphylococcus aureus-infected wounds.

Owing to its exposed nature, the skin can be injured by various factors, including by Staphylococcus aureus, which inhabits its innate microbiota. Treatment of infected wounds presents an important challenge, making it imperative to develop new treatment options. Plant-derived formulations, such as those containing Melaleuca alternifolia essential oil (MaEO), are used for wound treatment because of their healing, anti-inflammatory, and antimicrobial properties. This study presents a cream containing 2% MaEO (2% CMa) and evaluates its effects in an S. aureus-infected wound murine model. The 2% CMa was subjected to quality control testing and pH and analysis of density, organoleptic characteristics, and microbiological effects. The quality control parameters all revealed the good stability of the 2% CMa. The formulation strongly reduced the S. aureus ATCC 6538 colony-forming unit (CFU) count in an ex vivo porcine skin model. In the murine model, daily topical application of 2% CMa reduced the severity and size of S. aureus-infected wounds and the bacterial load. These effects may be due to the presence of terpinen-4-ol, which exhibits anti-inflammatory activity. Based on these findings, the formulation exhibits good quality and safety. We suggest the topical application of this formulation, which exhibited an antimicrobial effect, as an interesting treatment strategy for wound healing.

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.

The antimicrobial activity of tea tree oil (Melaleuca alternifolia) and its metal nanoparticles in oral bacteria.

Tea tree (Melaleuca alternifolia) oil (TTO) is an antimicrobial agent, and hence, its use in fabricating nanoparticles (NP) may be useful in providing more efficacious antimicrobial agents. The current research aimed to test the antimicrobial efficacy of TTO and its TTO-Metal-NPs against oral microbes: Porphyromonas gingivalis, Enterococcus faecalis, and Streptococcus mutans. The antimicrobial activity of TTO and zinc (Zn) and iron (Fe) nanoparticles (NPs) and the combined effects of antimicrobial agents were investigated using agar well diffusion assays. Fourier-transform infrared spectroscopy (FT-IR) was used to identify the phyto-constituents of TTO. Field emission scanning electron microscopy (FE-SEM), dynamic light scatter (DLS), and zeta potential were utilized to analyze the biogenic nanoparticles' morphology, size, and potential. The antimicrobial mode of action was determined by assessing the morphological changes under scanning electron microscopy (SEM). The TTO extracts converted Zn and Fe ions to NPs, having an average size of 97.50 (ZnNPs) and 102.4 nm (FeNPs). All tested agents had significant antibacterial efficacy against the tested oral microbes. However, the TTO extract was more efficacious than the NPs. Combination treatment of TTO with antibiotics resulted in partial additive effects against P. gingivalis and partial antagonistic effects against E. faecalis, S. mutans, and common mouthwashes (Oral B and chlorhexidine). TTO and NP-treated bacteria underwent morphological changes on treatment. M. alternifolia phytochemicals could be useful for further research and development of antimicrobial NPs. The current study highlights the variance in activity observed for different types of bacteria and antagonistic effects seen with common mouthwashes, which represent a threat to therapeutic efficacy and heighten the risk of clinical microbial resistance.

A comprehensive review on the pharmacological prospects of Terpinen-4-ol: From nature to medicine and beyond.

Owing to their extensive biological potential, essential oils (EOs) and their bioactive phytochemicals have gained attention from the scientific community. Within this domain, Terpinen-4-ol (T-4-ol), a bioactive monoterpene alcohol and the major constituent of tea tree oil (TTO), has made its way into translational research. Recent literature on T-4-ol strongly indicates its diverse pharmacological properties, including but not limited to antimicrobial, antivirulent, anti-oxidant, anti-inflammatory, anti-hypertensive, and anti-cancer effects. Hence, this review is the first to provide a comprehensive overview of the sources, bioavailability, safety, pharmaceutical delivery systems, and multifaceted biological properties of T-4-ol, emphasizing its medicinal potential for widescale application. The antibacterial and antifungal effectiveness of T-4-ol has been discussed, encompassing its role in combating a broad spectrum of bacterial and fungal pathogens. The review delves into the antivirulent prospects of T-4-ol, shedding light on its ability to attenuate virulence and mitigate bacterial pathogenesis. Scientific literature on the anti-oxidant and anti-inflammatory activity of T-4-ol highlighting its role in neutralizing reactive oxygen species and modulating inflammatory pathways has also been collated. Furthermore, the review elaborates on the cardioprotective and anti-hypertensive properties of T-4-ol and augments literature on its anti-cancer mechanism against various cancer cell lines. The review also provides in-depth knowledge of the pharmaceutical formulations of T-4-ol and recent knowledge about its application in clinical/field trials. The exploration of these diverse attributes positions T-4-ol as a promising candidate for further research and therapeutic repurposing in various biomedical applications.

Antifungal efficacy of natural antiseptic products against Candida auris.

Candida auris is an emerging fungal pathogen responsible for healthcare-associated infections and outbreaks with high mortality around the world. It readily colonizes the skin, nares, respiratory and urinary tract of hospitalized patients, and such colonization may lead to invasive Candida infection in susceptible patients. However, there is no recommended decolonization protocol for C. auris by international health authorities. The aim of this study is to evaluate the susceptibility of C. auris to commonly used synthetic and natural antiseptic products using an in vitro, broth microdilution assay. Synthetic antiseptics including chlorhexidine, povidone-iodine, and nystatin were shown to be fungicidal against C. auris. Among the natural antiseptics tested, tea tree oil and manuka oil were both fungicidal against C. auris at concentrations less than or equal to 1.25% (v/v). Manuka honey inhibited C. auris at 25% (v/v) concentrations. Among the commercial products tested, manuka body wash and mouthwash were fungicidal against C. auris at concentrations less than or equal to 0.39% (w/v) and 6.25% (v/v) of products as supplied for use, respectively, while tea tree body wash and MedihoneyTM wound gel demonstrated fungistatic properties. In conclusion, this study demonstrated good in vitro antifungal efficacy of tea tree oil, manuka oil, manuka honey, and commercially available antiseptic products containing these active ingredients. Future studies are warranted to evaluate the effectiveness of these antiseptic products in clinical settings.

Candida auris is an emerging superbug fungus that poses a serious threat to global public health. The excellent antifungal efficacy of natural antiseptics and their commercial hygiene products provide new insights into the development of an alternative decolonization regimen against C. auris.

Terpinen-4-ol from tea tree oil prevents Aspergillus flavus growth in postharvest wheat grain.

Plant volatile organic compounds (PVOCs) have gained increasing attention for their role in preventing fungal spoilage and insect contamination in postharvest agro-products owing to their effectiveness and sustainability. In this study, the essential oil was extracted from fresh M. alternifolia (tea tree) leaves, and the fumigation vapor of tea tree oil (TTO) completely inhibited the growth of Aspergillus flavus on agar plates at a concentration of 1.714 µL/mL. Terpinen-4-ol was identified as the major component (40.76 %) of TTO volatiles analyzed using headspace gas chromatography-mass spectrometry. Terpinen-4-ol vapor completely inhibited the A. flavus growth on agar plates and 20 % moisture wheat grain at 0.556 and 1.579 µL/mL, respectively, indicating that terpinen-4-ol serves as the main antifungal constituent in TTO volatiles. The minimum inhibitory concentration of terpinen-4-ol in liquid-contact culture was 1.6 µL/mL. Terpinen-4-ol treatment caused depressed, wrinkled, and punctured mycelial morphology and destroyed the plasma membrane integrity of A. flavus. Metabolomics analysis identified significant alterations in 93 metabolites, with 79 upregulated and 14 downregulated in A. flavus mycelia exposed to 1.6 µL/mL terpinen-4-ol for 6 h, involved in multiple cellular processes including cell membrane permeability and integrity, the ABC transport system, pentose phosphate pathway, and the tricarboxylic acid cycle. Biochemical analysis and 2,7-dichlorofluorescein diacetate staining showed that terpinen-4-ol induced oxidative stress and mitochondrial dysfunction in A. flavus mycelia. This study provides new insights into the antifungal effects of the main TTO volatile compounds terpinen-4-ol on the growth of A. flavus.

Tea tree oil inhibits hydrogen sulfide-induced oxidative damage in chicken lungs through CYP450s/ROS pathway.

A large amount of hydrogen sulfide (H2S) is produced in the process of chicken breeding, which can cause serious inflammation and oxidative damage to the respiratory system of chickens. Tea tree oil (TTO) has antioxidant and anti-inflammatory properties. No studies have been reported on the use of TTO in H2S-induced lung injury in chickens. Therefore, in this study, 240 one-day-old Roman pink laying hens were randomly and equally divided into 3 groups: control group (CON), H2S exposure group (AVG, containing H2S), and TTO treatment group (TTG, containing H2S and 0.02 mL/L TTO) to establish an experimental model of TTO treatment with H2S exposure for a period of 42 d. Hematoxylin and eosin (H&E) staining was used to detect lung histopathology. Gene expression profiles were analyzed using transcriptomics. The underlying mechanism of the amelioration of lung injury by TTO was further revealed by antioxidant enzyme assays and qRT-PCR. The results showed that H2S exposure induced significant gene expression of CYP450s (CYP1B1 and CYP1C1) (P < 0.05), and caused intense oxidative stress, apoptosis and inflammation compared with CON. TTO could reduce ROS production and enhance antioxidant capacity (SOD, CAT, T-AOC, and GSH-PX) by regulating the CYP450s/ROS pathway (P < 0.05). Compared with the control group, the treatment group showed significantly decreased expression of apoptotic (Caspase-8, Caspase-3, Bid and Fas) (P < 0.05) and inflammatory (IL-4, IL-16, NF-κB, TNF-α and IFN-γ) (P < 0.05) factors in the lung. This study revealed that TTO regulated CYP450s/ROS pathway to alleviate H2S-induced lung injury in chickens. These results enrich the theory of the action mechanism of TTO on H2S-exposed chicken lungs and are of great value for the treatment of H2S-exposed animals.

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.

Termites can learn.

It is generally believed that termites can't learn and are not "intelligent". This study aimed to test whether termites could have any form of memory. A Y-shaped test device with one release chamber and two identical test chambers was designed and constructed by 3D printing. A colony of damp wood termites was harvested from the wild. Worker termites were randomly selected for experiment. Repellent odors that could mimic the alarm pheromone for termites were first identified. Among all substances tested, a tea tree oil and lemon juice were found to contain repellent odors for the tested termites, as they significantly reduced the time that termites spent in the chamber treated with these substances. As control, a trail pheromone was found to be attractive. Subsequently, a second cohort of termites were operant conditioned by punishment using both tea tree oil and lemon juice, and then tested for their ability to remember the path that could lead to the repellant odors. The test device was thoroughly cleaned between trials. It was found that conditioned termites displayed a reduced tendency to choose the path that led to expectant punishment as compared with naïve termites. Thus, it is concluded that damp wood termites are capable of learning and forming "fear memory", indicative of "intelligence" in termites. This result challenges established presumption about termites' intelligence.

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.

Laboratory assessment of the acaricidal, repellent and anti-cholinesterase effects of Melaleuca alternifolia and Chamaemelum nobile essential oils against Hyalomma scupense ticks.

In cattle, Hyalomma scupense serves as an important vector of several pathogens resulting in diseases, subsequently affecting the agricultural field as well as the economy. Resistance to chemical acaricides has become widespread affirming the need for new drugs to tick control. The goal of this study was to investigate the acaricidal, repellent activities as well as the putative mode of action of two essential oils (EOs) from Melaleuca alternifolia (Tea tree) and Chamaemelum nobile (Roman chamomile) on Hyalomma scupense. The chemical composition of EOs was also evaluated. Different concentrations of EOs were tested in vitro for their acaricidal property on adults and larvae of H. scupense using adult immersion test (AIT) and larval packet test (LPT). Additionally, using Ellman's spectrophotometric method, the anticholinesterase (AChE) inhibition activity of M. alternifolia and C. nobile EOs was assessed in order to understand their putative mode of action. The main compounds of C. nobile were α-Bisabolene (22.20%) and (E)-ß-Famesene (20.41%). The major components in the analyzed M. alternifolia were Terpinen-4-ol (36.32%) and γ-Terpinene (13.69%). Adulticidal and larvicidal assays demonstrated a promising efficacy of the essential oils against tick H. scupense. The lethal concentration (LC50) values obtained for M. alternifolia and C. nobile oils were 0.84 and 0.96 mg/mL in the AIT and 0.37 and 0.48 mg/mL in the LPT, respectively. Regarding repellent activity, M. alternifolia achieved 100% repellency at the concentration of 1 mg/mL while C. nobile showed 95.98% repellency activity at concentration of 4 mg/mL. Also, M. alternifolia and C. nobile EOs displayed potent AChE inhibition with IC50 value of 91.27 and 100.12 µg/mL, respectively. In the present study, M. alternifolia and, to a lesser degree, C. nobile EOs were found to be effective in vitro acaricides, repellents and acetylcholinesterase inhibitor against H. scupense ticks. These plants may represent an economical and sustainable alternative to toxic synthetic acaricides in the management of ectoparasites of veterinary importance.

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.

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.

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.

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.

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.

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.