Antibacterial Effects of Essential Oils on P. aeruginosa, Methicillin-Resistant S. aureus, and Staphylococcus spp. Isolated from Dog Wounds

<b>Background</b>: Essential oils exhibit several biological activities such as antimicrobial, antioxidant, proliferative, and anti-inflammatory. This study was aimed at investigating the antimicrobial effects and cytotoxic activities of niaouli, palmarosa, and clove essential oils. <b>Methods</b>: Content analyses of these essential oils were carried out by gas chromatography-mass spectrometry. The antibacterial activity was screened against methicillin-resistant <i>S. aureus</i> ATCC 43300, <i>P. aeruginosa</i> ATCC 27853, <i>P. aeruginosa</i> PAO1, <i>S. aureus</i> ATCC 25923, and 44 isolates (22 <i>P. aeruginosa</i> isolates, 4 <i>S. aureus</i> isolates, and 18 <i>Staphylococcus</i> spp. isolates) obtained from dogs with previous wound infections who were included in the current study. The antimicrobial effects of essential oils were investigated using disk diffusion and minimum inhibition/bactericidal concentration methods. Additionally, the antibiofilm, protease, elastase, and gelatinase activities of the essential oils were evaluated. Different concentrations of each essential oil ranging from 10 to 1000 µg/mL were also analyzed in terms of cell viability by WST-8 assay in primary canine fibroblast cells. <b>Results:</b> The fibroblast cell viabilities of palmarosa, niaouli, and clove oils at a 1000 µg/mL concentration were 75.4%, 96.39%, and 75.34%, respectively. All the EOs were found to have bactericidal effects with MBCs/MICs of 0.015 to 0.5 µL/mL against <i>P. aeruginosa</i>, <i>Staphylococcus</i> isolates (<i>p</i> < 0.001). Palmarosa was found to have the largest inhibition zone diameter (20.5 ± 6.6, 16.4 ± 2.3) compared to other essential oils in the disk diffusion test against <i>Staphylococcus</i> spp. and <i>P. aeruginosa</i> (<i>p</i> < 0.001). But none of the EOs reduced protease, elastase, and gelatinase activities, which are some of the virulence properties of the tested bacteria. <b>Conclusions:</b> These results showed that palmarosa, niaouli, and clove essential oils act as potential antibacterial agents for dogs against <i>P. aeruginosa</i>, methicillin-resistant <i>S. aureus</i>, and <i>Staphylococcus</i> spp., without damaging the skin.