Antimicrobial and anti-inflammatory effects of Eugenia brejoensis essential oil in mice wounds infected by Staphylococcus aureus

Abstract

Eugenia brejoensis Mazine (Myrtaceae) is source of an essential oil (EbEO) with anti-infective activities against Staphylococcus aureus. This study evaluated the antimicrobial and anti-inflammatory potentials of EbEO in S. aureus-infected skin wounds. The excisional lesions (64 mm²) were induced on Swiss mice back (6 to 8-week-old) that were allocated into 3 groups (n = 12): 1) non-infected wounds (CON); 2) wounds infected with S. aureus ATCC 6538 (Sa); 3) S. aureus-infected wounds and treated with EbEO (Sa + EbEO). The infected groups received approximately 10⁴ CFU/wound. The animals were treated with EbEO (10 µg/wound/day) or vehicle from the 1-day post-infection (dpi) until the 10th dpi. The clinical parameters (wound area, presence of exudate, edema intensity, etc.) were daily analyzed. The levels of inflammatory mediators (cytokines, nitric oxide, VEGF) and bacterial load were measured at the cutaneous tissue at 4th dpi and 10th dpi. Topical application of EbEO accelerated wound contraction with an average contraction of 83.48 ± 11.27 % of the lesion area until 6th dpi. In this period, the rates of lesion contraction were 54.28 ± 5.57% and 34.5 ± 2.67% for CON and Sa groups, respectively. The positive effects of EbEO on wound contraction were associated with significantly (p < 0.05) reduction on bacterial load and the release of inflammatory mediators (IL-6, IL-17A, TNF-α, NO and VEGF). Taken together, these data confirm the antimicrobial potential of EbEO and provide insights into its anti-inflammatory effects, making this essential oil an interesting candidate for the development of new therapeutic alternatives for infected cutaneous wounds.

Keywords: caatinga plants; host-pathogen interactions; infectious diseases; inflammatory mediators; skin healing; volatile compounds.

FIGURE 1

Effects of topical treatment with Eugenia brejoensis essential oil on skin lesion contaminated by Staphylococcus aureus. (A) Representative images of wounds contraction evolution; (B) Relative wound contraction values obtained during the 10 days of analysis; (C) Area under curve (AUC) of data obtained from wound contraction; (D) Analysis of the clinical parameters of the experimental groups during the clinical evaluation period. (E) Analysis of the area under the curve (AUC) of the clinical parameters of the mice. (@) Statistical differences of PBS-treated infected wound area (Sa group) and other experimental groups (CON and Sa + Cramoll groups) (p < 0.001); (#) Statistical differences of PBS-treated infected wound area (Sa group) and Cramoll-treated infected wounds (Sa + Cramoll group) (p < 0.01). *p < 0.05; **p < 0.01; ***p < 0.001; ***p < 0.0001.

FIGURE 2

Histological evaluation of topical treatment with EbEO. (A) Analysis of wound tissues without S. aureus inoculation (CON group); (B) Analysis of wound tissues infected by S. aureus and without treatment (Sa group); (C) Analysis of wound tissues infected by S. aureus and treated by EbEO (Sa + EbEO group). The intense proinflammatory infiltrated are highlighted by arrow. 40 X.

FIGURE 3

Effect of topical treatment with Eugenia brejoensis essential oil on bacterial load in the tissue of wounds contaminated by Staphylococcus aureus. (A) Bacterial load after 3 days of treatment; (B) Bacterial load after 10 days of treatment. **p < 0.05; ***p < 0.001; ****p < 0.0001.

FIGURE 4

Effect of topical treatment with Eugenia brejoensis essential oil on inflammatory markers present in the tissue of wounds contaminated by Staphylococcus aureus. (A) Amount of IL-6 at wound tissue; (B) Amount of IL-17A at wound tissue; (C) Amount of TNF-α at wound tissue; (D) Amount of NO at wound tissue; (E) Amount of VEGF at wound tissue. *p < 0.05; **p < 0.01; ****p < 0.0001.