Characterization of Canine Otitis Externa Pseudomonas aeruginosa Isolates and Their Sensitivities to Different Essential Oils

Otitis externa is common infection in dogs. Its most important aetiologic agent is <i>Pseudomonas aeruginosa</i>, which, besides its ability to form biofilm, can also be resistant to several antibiotics, leading to therapeutic failures in several cases. Promising therapeutic alternatives are constantly being sought to treat chronic, recurrent infections. Within the framework of this study, we investigated the antibacterial potential of essential oils against canine isolates of <i>P. aeruginosa</i>. Forty <i>P. aeruginosa</i> were isolated from individual dogs' otitis externa. They were identified by MALDI-TOF MS, their antibiotic susceptibility was determined with disk diffusion, and their genetic relatedness was established using pulsed-field gel electrophoresis. Fifty-seven essential oils were screened for their antipseudomonas effects using the drop plate method, and six essential oils-cinnamon (bark and leaf), bay, rosemary, thyme, and bitter orange-were further tested for their mature-biofilm-degrading capacities at 30 °C and 37 °C. Even though the molecular relatedness of the forty <i>P. aeruginosa</i> isolates could be excluded, all isolates' growth was inhibited and their biofilms degraded by a 2.5% concentration of cinnamon (bark and leaf), bay, rosemary, thyme, or bitter orange essential oil. Our results show that essential oils are potent alternatives in the treatment of otitis externa.