In vitro antimycoplasmal activity of Melaleuca alternifolia essential oil

Clinical evaluation of an antiinflammatory and antioxidant diet effect in 30 dogs affected by chronic otitis externa: preliminary results

The aim of this evaluation study was to assess the possible role of a specific nutraceutical diet in relieving main clinical symptoms of chronic bilateral otitis externa (occlusion of ear canal, erythema, discharge quantity, and odor) in 30 adult dogs. Thirty dogs of different breeds (mean age ± SEM; 6.03 ± 0.15 years and mean weight ± SEM; 32.01 ± 1.17 Kg; 53.3% males, 46.6% females) with evident chronic clinical otitis symptoms were equally divided and randomly assigned to receive either the nutraceutical diet (ND group) or a standard diet (SD group) over a period of 90 days. In all cases a topical pharmacological treatment was given. The nutraceutical diet, also endowed with anti-inflammatory and antioxidant activities, significantly decreased the mean score intensity of all symptoms after 90 days of intervention (P < 0.0001) with the exception of Malassezia pachydermatis infection which was only slightly reduced. Our investigation is one of the few evidence-based results where a commercial nutraceutical diet has been proven effective, in combination with drugs, in relieving otitis externa-related symptoms. This study opens new insights into otitis externa clinical management providing evidence of efficacy of a combined therapy with drugs and a specific nutraceutical diet.

In vitro activity of essential oils of free and nanostructured Melaleuca alternifolia and of terpinen-4-ol on eggs and larvae of Haemonchus contortus

Haemonchus contortus is one of the major gastrointestinal nematodes responsible for significant economic and production losses of sheep. Diseases caused by this species lack effective anthelmintic products, and the search for new compounds to replace synthetic anthelmintics has been extensive. The present investigation assesses the in vitro activity of the essential oil of melaleuca (Melaleuca alternifolia), both free (TTO) and nanostructured (nanoTTO), and terpinen-4-ol (terp-4-ol) on eggs and larvae of H. contortus. Tests of egg hatching (EHT) and inhibition of larval migration (LMIT) were used to assess the in vitro efficacy of TTO, nanoTTO and terp-4-ol. Using EHT, at a concentration of 3.5 mg/ml, 100% inhibition occurred using TTO and terp-4-ol, with LC50 values of 0.43 and 0.63 mg/ml, and LC90 values of 1.75 mg/ml and 3.12 mg/ml, respectively. NanoTTO had lower activity, with 82.6% inhibition at the same concentration. Using LMIT, TTO and nanoTTO had a similar activity with 88.0% and 84.8% inhibition, respectively, at a concentration of 56 mg/ml. Terp-4-ol had a greater effect on larvae, with 85.7% inhibition at a concentration of 56 mg/ml and 82.4% at 3.5 mg/ml, demonstrating high activity at the lowest concentration tested. Therefore, the results indicate that all substances tested showed ovicidal and larvicidal activity against H. contortus. TTO, terp-4-ol and, mainly, nanoTTO may be targeted in in vivo studies, besides being a promising line of research into the control and treatment of veterinary important helminths.

Effect of tea tree oil (Melaleuca alternifolia) on the longevity and immune response of rats infected by Trypanosoma evansi

This study aimed to evaluate the effect of tea tree oil (TTO - Melaleuca alternifolia) on hepatic and renal functions, and the immune response of rats infected by Trypanosoma evansi. A pilot study has shown that rats treated with TTO orally (1 ml kg(-1)) had increased survival rate without curative effect. In order to verify if increased longevity was related to a better immune response against T. evansi when using tea tree oil, a second experiment was conducted. Thus, twenty-four rats were divided into four groups. The groups A and B were composed of uninfected animals, and the groups C and D had rats experimentally infected by T. evansi. Animals from the groups B and D were treated orally with TTO (1 ml kg(-1)) for three days. Blood samples were collected to verify humoral response analysis for immunoglobulins (IgA, IgM, IgE, and IgG) and cytokines (TNF-α, INF-γ, IL-1, IL-6, IL-4, and IL-10) at days 0, 3, 5 and 15 post-infection (PI). TTO treatment caused changes in the immunoglobulins and cytokines profile, as well as the course of T. evansi infection in rats. It was found that the TTO was not toxic, i.e., hepatic and renal functions were not affected. Therefore, it is possible to conclude that TTO influences the levels of inflammatory mediators and has trypanocidal effect, increasing life expectancy of rats infected by T. evansi.

Development and characterization of essential oil component-based polymer films: a potential approach to reduce bacterial biofilm

The development of new polymeric materials aimed to control the bacterial biofilm appears to be an important practical approach. The goal of the present study was to prepare and characterize poly(ethylene-co-vinyl acetate) copolymer (EVA) films containing citronellol, eugenol, and linalool and evaluate their efficiency on growth and biofilm formation of Listeria monocytogenes, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa in monospecies and dual species. The results showed that the addition of oil components influenced the elastic modulus (15 % decrease), the tensile stress (30 % decrease), the elongation at break (10 % increase), and the contact angle values (10-20° decrease) while leaving the homogeneity of the surface unaltered. Among the polymeric films, EVA + citronellol and EVA + eugenol at 7 wt% had the best inhibitory effect. After 24-48 h of incubation, EVA + citronellol was more effective against the growth (30-60 % reduction) than EVA + eugenol (15-30 % inhibition). However, this inhibition decreased after 240 h of incubation. On the contrary, the biofilm evaluation revealed a strong inhibition trend also after prolonged incubation time: the amount of biomass per square centimeter formed on copolymer with oil components was significantly less (40-70 % decrease) than that on pure copolymer control for L. monocytogenes, S. aureus, and E. coli. When polymeric materials were simultaneously inoculated with combinations of S. aureus and E. coli, the biomass accumulated was higher for EVA + citronellol and lower for EVA + eugenol than that in monoculture biofilm. The findings were similar to the results obtained by 2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide assay that measures the metabolic activity of viable cells.

[Efficacy of plant products against herpetic infections]

Essential oils from various aromatic medicinal plants are highly active against some viral infections, e.g. labial herpes caused by herpes simplex virus type 1. Balm oil, tea tree oil and peppermint oil demonstrate in vitro a significant antiherpetic activity, mainly related to a direct drug-virus particle interaction, some essential oils also act directly virucidal. Interestingly, these essential oils are also highly active against acyclovir-resistant herpes simplex virus strains. In clinical studies, tea tree oil has been shown to possess antiherpetic, anti-inflammatory and pain-relieving properties, as well as to accelerate the healing process of herpes labialis. Applying diluted essential oils three to four times daily for the antiherpetic treatment of affected areas is recommended. Some companies have marketed plant products, e.g. from Melissa, for the treatment of recurrent herpetic infections.

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.