Antibacterial and Antifungal Activity of Essential Oils against Pathogens Responsible for Otitis Externa in Dogs and Cats

Abstract

<b>Background:</b> Essential oils (EOs) are recommended by some veterinarians to treat otitis externa in pets, but data about their efficacy in scientific literature are very scant. <b>Methods:</b> Nine commercial EOs, from roman chamomile (<i>Anthemis nobilis</i> L.), star anise (<i>Illicium verum</i>), lavender (<i>Lavandula hybrida</i>), litsea (<i>Litsea cubeba</i> (Lour.) Pers.), basil (<i>Ocimum basilicum</i> L.), oregano (<i>Origanum vulgare</i> L. subsp. <i>hirticum</i>), rosemary (<i>Rosmarinus officinalis</i> L.), clary sage (<i>Salvia sclarea</i> L.), and thyme (<i>Thymus vulgaris</i> L.) were tested against bacterial and fungal pathogens previously isolated from dogs and cats with otitis externa. In particular, the analyses were carried out against <i>Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus pseudointermedius</i>, <i>Aspergillus niger, Aspergillus fumigatus, Aspergillus terreus, Candida albicans, Candida tropicalis, Trichosporon</i> sp., and <i>Rhodotorula</i> sp. <b>Results:</b><i>O. vulgare</i> and <i>S. sclarea</i> showed superior antibacterial activity, even if not against all the strains. <i>Trichosporon</i> sp., <i>C. albicans</i>, and <i>A. terreus</i> were insensitive to most Eos, while other yeasts and molds showed different degrees of sensitivity. In particular, most fungi were inhibited by <i>O. vulgare</i> and <i>R. officinalis</i>. <b>Conclusions:</b> The obtained results suggest that some EOs could be included in treatment as an alternative therapeutic option in bacterial otitis complicated by fungi, in association with conventional drugs.