Effect of tea tree essential oil (Melaleuca Alternifolia) on the control of bacteria isolated from the uterus of a mare with endometritis

Introduction: Endometritis are considered the main causes of subfertility and infertility in the equine species. The use of antimicrobials is essential for the successful treatment of the condition. However, indiscriminate use has resulted in the development of microbial resistance. Melaleuca essential oil (Melaleuca alternifolia) has proven effectiveness in microbial control due to its antibacterial, antiviral and antifungal properties. Faced with the need to seek new treatment alternatives and the scarcity of studies on the action of tea tree oil against pathogens that cause endometritis, the present study aimed to evaluate the antimicrobial effect of tea tree essential oil in vitro in the control of bacteria isolated from the uterus of a mare with endometritis, comparing the action of antibiotics commonly used as treatment.

Material and methods: Samples collected from the endometrium of a mare with endometritis were submitted to microbiological culture. Susceptibility to antimicrobials and oil was determined by the qualitative method of minimum inhibitory concentration established by CLSI (2019). An antibiogram was performed with gentamicin, enrofloxacin and ceftiofur, and tea tree oil at 100% concentrations; 50%; 25%; 12.5%; 6.75%; 3.37%; 1.68% and 0.84%.

Results and Discussion: The strains found were consistent with Bacillus cereus and Staphylococcus aureus. The diameters of the inhibitory halos obtained were: negative control (DMSO and saline solution) absent, gentamicin (16mm), enrofloxacin (21mm) and ceftiofur (22mm) consistent with the values imposed by NCCLS (2003). In the group treated with oil there was an inhibitory halo only at concentrations of 100% (20mm), 50% (11mm) and 25% (8mm). In the other concentrations there was resistance of the strains. Petry et al. (2021), evaluating the antimicrobial action of the same oil, considered sensitivity of strains in halos from 8mm.

Conclusion: Melaleuca essential oil in a concentration greater than 25% showed an antimicrobial effect against strains that cause endometritis.

References

1. CLSI - Clinical and laboratory standards institute. Manual de Antibiograma. Laborclin Produtos para Laboratórios Ltda. Rev 16 – 03/2019.
2. NCCLS. Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard - Eighth Edition. NCCLS document M2-A8 (ISBN 1-56238-485-6). NCCLS, 940 West Valley Road, Suite 1400, Wayne, Pennsylvania 19087-1898 USA, 2003.
3. Petry T F et al. Atividade antimicrobiana de biofilme de quitosana associado ao óleo essencial de citrus reticulata. Mostra de Extensão, Ciência e Tecnologia da Unisc, n. 2, p. 184, 2021.
4. *The present study was approved by the Ethics Committee on the Use of Animals of the Federal University of Espírito Santo, under number 011/2022.