Minimum inhibitory concentration of essential oils against Staphylococcus aureus isolated from dogs with external otitis

Geraldo Márcio Costa, Ingrid Alexandre Prado, Glei dos Anjos de Carvalho-Castro, Glaúcia Frasnelli Mian, Carlos Artur Lopes Leite, Dircéia Aparecida Costa Custódio, Roberta Hilsdorf Piccoli


Canine otitis externa is a disease that affects the external acoustic meatus of about 20% of dogs at some point in life, without predilection for race, age, or sex. It is a multifactorial disease whose etiology involves several microorganisms, detaching Staphylococcus aureus. Antimicrobials are the basis for treating this illness; however, due to the increase in antimicrobial resistance, conventional drugs have become ineffective, requiring the search for alternative therapies. In this context, essential oils (EOs) have great therapeutic potential due to their broad antimicrobial action. This study aimed to evaluate the minimum inhibitory concentration (MIC) in order to measure the MIC50 and MIC90 of gentamicin and EOs of Eugenia caryophyllata, Thymus vulgaris, Cymbopogon winterianus, Cymbopogon citratus, and Cinnamomum cassia against 62 Staphylococcus aureus strains isolated from the external acoustic meatus of dogs. All EOs showed antibacterial action against the studied microorganisms, and their MIC50 and MIC90 were as follows: Eugenia caryophyllata, 2.42 mg mL-1 and 7.25 mg mL-1; Thymus vulgaris, 9.51 mg mL-1 and 22.94 mg mL-1; Cymbopogon winterianus, 26.78 mg mL-1 and 157.79 mg mL-1; Cinnamomum cassia and Cymbopogon citratus, lower than 16.48 and 27.81 mg mL-1, with the same MIC for all isolates. The MIC50 and MIC90 found for gentamicin were 1ug mL-1and 8 ug mL-1. The MIC range found to antibiotic in this assay was 0.5 ug mL-1to 128 ug mL-1, and the isolates were classified as susceptible [48 strains (77.41%) - MIC range of 0.5-4.0 ug mL-1], intermediate [eight strains (12.90%) - (MIC = 8.0 ug mL-1], or resistant [six strains (9.68%) - MIC bigger, smaller 16 ug mL-1]. The results, according to the in vitro assays, showed that resistance to gentamicin, one of the antimicrobials most commonly used to treat canine otitis, is present in the Staphylococcus aureus population evaluated. Additionally, the tested EOs have great potential for therapeutic use, however future studies should be carried out to evaluate their in vivo efficacy.


Phytotherapy; Otopathies; Antibacterials; Natural antimicrobials; MIC.

Full Text:



Aiemsaard, J., Aiumlamai, S., Aromdee, C., Taweechaisupapong, S., & Khunkitti, W. (2011). The effect of lemongrass oil and its major components on clinical isolate mastitis pathogens and their mechanisms of action on Staphylococcus aureus DMST 4745. Research in Veterinary Science, 91(3), 31-37. doi: 10.10 16/j.rvsc.2011.01.012

Akhtar, M. S., Degaga, B., & Azam, T. (2014). Antimicrobial activity of essential oils extracted from medicinal plants against the pathogenic microorganisms: “a review”. Biological Sciences and Pharmaceutical Research, 2(1), 1-7. Retrieved from

Al-Mariri, A., & Safi, M. (2014). In vitro antibacterial activity of several plant extracts and oils against some gram-negative bacteria, Iranian Journal of Medical Sciences, 39(1), 36-43. Retrieved from https://www.

Al-Shabib, N. A., Husain, F. M., Ahmad, I., & Baig, M. H. (2017). Eugenol inhibits quorum sensing and biofilm of toxigenic MRSA strains isolated from food handlers employed in Saudi Arabia. Biotechnology & Biotechnological Equipment, 31(2), 387-396. doi: 10.1080/13102818.2017.1281761

Andrade, B. F. M. T., Barbosa, L. N., Probst, I. S., & Fernandes Júnior, A. (2014). Antimicrobial activity of essential oils. Journal of Essential oil Research, 26(1), 34-40. doi: 10.1080/10412905.2013.860409

Baskaran, S. A., Kazmer, G. W., Hinckley, L., Andrew, S. M., & Venkitanarayanan, K. (2009). Antibacterial effect of plant-derived antimicrobials on major bacterial mastitis pathogens in vitro. Journal of Dairy Science, 92(4), 1423-1429. doi: 10.3168/jds.2008-1384.


Semina: Ciênc. Agrár.
Londrina - PR
E-ISSN 1679-0359
DOI: 10.5433 / 1679-0359
Este obra está licenciado com uma Licença  Creative Commons Atribuição-NãoComercial 4.0 Internacional