The worldwide problem of infectious diseases has appeared in recent years, and antimicrobial agents are crucial in reducing disease emergence. Nevertheless, the development and distribution of multidrug-resistant (MDR) strains in pathogenic bacteria, such as Escherichia coli, Staphylococcus aureus, Salmonella Typhi and Citrobacter koseri, has become a major society health hazard. Essential oils could serve as a promising tool as a natural drug in fighting the problem with these bacteria. The current study aimed to investigate the antimicrobial effectiveness of tea tree (Melaleuca alternifolia (Maiden and Betche) Cheel), rosemary (Rosmarinus officinalis L.), eucalyptus (Eucalyptus obliqua L’Hér.), and lavender (Lavandula angustifolia Mill) essential oils. The antimicrobial properties of essential oils were screened against four pathogenic bacteria, E. coli, S. aureus, S. Tyhpi, and C. koseri, and two reference bacterial strains, while for the testing, the agar well diffusion method was used. Gas chromatography (GC) and gas chromatography–mass spectrometric (GC–MSD) analyses were performed on essential oils. The obtained results showed that M. alternifolia essential oil is the richest in terpinen-4-ol, R. officinalis and E. oblique essential oils in 1,8-cineole, and L. angustifolia essential oil in α-terpinyl acetate. In addition, the main bioactive compounds present in the essential oil of tea tree are rich in α-pinene (18.38%), limonene (7.55%) and γ-terpinene (14.01%). The essential oil of rosemary is rich in α-pinene (8.38%) and limonene (11.86%); eucalyptus essential oil has significant concentrations of α-pinene (12.60%), p-cymene (3.24%), limonene (3.87%), and γ-terpinene (7.37%), while the essential oil of lavender is rich in linalool (10.71%), linalool acetate (9.60%), α-terpinyl acetate (10.93%), and carbitol (13.05%) bioactive compounds, respectively. The obtained results from the in vitro study revealed that most of the essential oils exhibited antimicrobial properties. Among the tested essential oils, tea tree was discovered to demonstrate the strongest antimicrobial activity. The recorded MIC of S. Typhi was 6.2 mg/mL, 3.4 mg/mL of C. koseri, 3.1 mg/mL of E. coli, and 2.7 mg/mL of E. coli ATCC 25922, compared to M. alternifolia. Similarly, only S. aureus ATCC 25923 showed antimicrobial activity towards R. officinalis (1.4 mg/mL), E. oblique (2.9 mg/mL), and L. angustifolia (2.1 mg/mL). Based on the obtained results, it is possible to conclude that tea tree essential oil might be used as an ecological antimicrobial in treating infectious diseases caused by the tested pathogens.

The aim of this review paper is to review the data on tea tree (Melaleuca alternifolia) as an antimicrobial, antioxidant and acaricidal in poultry production. Tea tree exhibits a wide spectrum of antimicrobial activities with minimal inhibitory concentrations between 0.12 and 4 mg/ml. Its modes of action against Gram-negative bacterium Escherichia coli (0.12 to 1.5 mg/ml), Gram-positive bacterium Staphylococcus aureus (0.12 to 1 mg/ml), Aspergillus fumigatus (1.78 mg/ml) and yeast, Candida albicans (0.05 to 0.5 mg/ml) have been investigated using a range of different methods. As an antimicrobial, tea tree has high antifungal, bacteriostatic and germicidal activity (e.g. a decrease of 73.8% in Candida sp.), because of its components such as terpinen-4-ol, α-terpineol, linalool, α-pinene, β-pinene, β-myrcene and 1,8-cineole. Its bioactive compounds such as α-terpinene, α-terpinolene and γ-terpinene show high antioxidant activity when applied in concentrations of 100 and 200 μl/ml, while its essential oils demonstrated free radical scavenging activity of 60 to 80%. Tea trees insecticidal and acaricidal properties have been tested for tick control. The mortality of ticks (Ixodes ricinus) and poultry red mites (Dermanyssus gallinae) have been recorded at levels over 60% and 80%, respectively, when used in concentrations of 0.15 to 0.30 mg/cm2 during in vitro testing, and in vivo, when sprayed in poultry houses. When tea tree was used in a form of essential oils as a dietary supplement in concentrations of 50 to 150 mg/kg in broiler chicken diets, a significant increase in daily weight (by around 7%) and decrease in morbidity and mortality were seen. Additionally, when applied in laying hen nutrition, a significant increase in daily egg production has been recorded. Tea tree essential oils when supplemented in poultry diets have high positive effects regarding productivity performance, but this requires further field experiments to clarify standardisation of the material and effective inclusion levels.

The food of animal origin that is the most consumed is the table egg, but laying hens treated with antibiotics can produce eggs contaminated with antibiotic residues. Residues of antibiotics may present a risk for consumer health. Keeping in mind that laying hens almost always suffer from Mycoplasma (Mycoplasma synoviae), for which they are treated with antibiotics, high-quality egg production is even harder. Our research aimed to investigate the influence of three different antibiotics compared to the tea tree (Melaleuca alternifolia) essential oil administered to naturally infected laying hens with M. synoviae, on antibiotic residues in eggs as well as the egg nutritive and sensory qualities. A total of 20,000 laying hens, housed in one facility and divided into four lines each consisting of 5000 hens naturally infected with M. synoviae, was used. For the antimicrobial therapy, tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) were used, respectively. As a control, tea tree essential oil (TT) was used. Based on the gained results all tetracyclines treatment residue values were significantly (p < 0.05) higher compared to the control treatment (TT), but without any significant differences (p > 0.05) between themselves. The results showed no differences in the nutritive and the sensory qualities of eggs between the control and the experimental treatments (p > 0.05). Keeping in mind the obtained results from this study, it can be concluded that tea tree essential oil could be successfully used as a natural antibiotic in the treatment of M. synoviae, without any adverse effects on table egg quality.

The level of production in a variety of organic production systems is often lower than in other traditional production systems. In poultry production, there is also a direct negative effect of the small scale regarding sustainable organic poultry production. Regardless of differences between organic and conventional production systems, this experiment aimed to investigate the usage of tea tree Melaleuca alternifolia (Maiden and Betche) Cheel essential oils as a natural alternative to antibiotics in hen nutrition on productive parameters, table egg quality and eggs fatty acid profile as a promising sustainable organic agricultural tool. A total of 360 Lohmann Brown hens, aged 54 weeks, divided into three different treatment diets, were supplemented with 0 (T1), 40 (T2) and 80 mg/kg (T3) of M. alternifolia essential oil, respectively. Experimental treatments were replicated four times within 30 birds each. The experiment lasted for a total of 56 days (55 to 62 weeks of hens age). A 56-day experimental had two timetable periods of 28 days each: period 1 (55 to 58 weeks of hen age) and period 2 (59 to 62 weeks of hen age). For compound feed supplemented with M. alternifolia essential oil, daily egg production and the efficiency of nutrient utilization (FCR) was improved significantly (p < 0.05) until the end of week 58, with a significant (p < 0.05) increase in the thickness of eggshell, as well as egg production (p < 0.05). However, egg mass, feed consumption, FCR and albumen height, Haugh unit, and eggshell strength did not show any significant (p > 0.05) differences influenced by essential oil feed supplementation. Lower concentrations of saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA), and higher concentrations of polyunsaturated fatty acid (PUFA), were recorded with M. alternifolia essential oil supplementation, but without significant (p > 0.05) differences. At the end of the experiment, the obtained results showed that the addition of M. alternifolia essential oil to hen nutrition had a positive effect on production parameters and eggs fatty acid profile, with increased eggshell thickness (p < 0.05).