In vitro action of melaleuca alternifolia oil against bacteria and fungi isolated from semen and urethral fossa of stallion

Introduction: The action of essential oils has been explored in an attempt to overcome antimicrobial resistance. Tea tree essential oil (Melaleuca alternifolia) is considered excellent ally in microbial control due to its antibacterial, antiviral and antifungal properties. Given the scarcity of studies on its effects in the treatment of genital infections in stallions, this study proposed to evaluate the antimicrobial activity of tea tree essential oil in vitro, compared to the action of commonly used antibiotics and antifungals, against microorganisms isolated from semen and urethral fossa of stallions.

Material and Methods: Samples collected from the urethral fossa and semen of a stallion were submitted to microbiological culture. Antibiogram was performed with ceftiofur, ampicillin, enrofloxacin, ketoconazole and itraconazole. Susceptibility to antimicrobials and tea tree essential oil was determined by the qualitative method of minimum inhibitory concentration established by CLSI (2019).

Results: Bacterial colonies suggestive of Bacillus cereus, Staphylococcus and Micrococcus spp. and fungal colonies were isolated. The isolated strains were resistant to enrofloxacin, ketoconazole and itraconazole, showing senility only to ceftiofur and ampicillin. Regarding the bactericidal power of the oil, the inhibitory halo at concentrations of 100% and 50% was 10 mm, similar to the halo generated by ceftiofur, and higher than that of enrofloxacin, showing a satisfactory effect against the isolated bacteria. Concentrations of 25%, 12.5% and 6.25% did not demonstrate antimicrobial action. Regarding the fungicidal action, a more satisfactory result was obtained at a concentration of 100%, whose halo of 27 mm, demonstrated antifungal effect higher than standard established (CLSI, 2019).

Discussion/Conclusion: Tea tree essential oil presented as a promising antimicrobial agent, constituting an efficient alternative in the treatment of pathogens isolated from the genital system of stallions. These results corroborate with Neves et al. (2018), who observed the efficacy of oil against the same microorganisms.

References

1. CLSI - Clinical and laboratory standards institute. Manual de Antibiograma. Laborclin Produtos para Laboratórios Ltda. Rev 16 –03/2019.
2. Neves R et al. In vitro and in vivo efficacy of tea tree essential oil for bacterial and yeast ear infections in dogs. Pesquisa Veterinária Brasileira, v. 38, n. 8, p. 1597- 1607, 2018.
3. 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.