Antifungal Activity of Natural Essential Oils against Molds and Yeasts Associated with Respiratory Problems in Broiler Chickens

In recent years, essential oils (EOs) have been investigated for their antifungal activity which could predict therapeutic benefits for fungal diseases as an excellent alternative for the chemical medication. In this study, the antifungal activity of different concentrations (0.05, 0.1, 0.2, 0.3, and 0.5%) of thyme, anise, and cinnamon EOs was performed against of 51 fungal isolates (36 molds and 15 yeasts) recovered from broiler chickens using the agar dilution method. Thyme oil inhibited the growth of all tested isolates at concentrations of 0.5, 0.3, and 0.2% while concentration of 0.1% inhibited the growth of 100% of A. niger and C. albicans isolates as well as 40 and 81.2% of A. flavus and A. fumigatus isolates, respectively. Cinnamon oil inhibited the growth of all tested isolates except at 0.05% concentration which inhibited only 40, 20, 62.5 and 86.7% of A. niger, A. flavus, A. fumigatus, and C. albicans isolates, respectively. The anise oil had the lowest activity and 0.5% concentration only inhibited completely the fungal growth. Additionally, 8 isolates were selected and subjected to the Internal Transcribed Spacer (ITS) gene-based PCR, sequencing, and comparative sequence analyses. PCR results confirmed the morphotypic identification of fungal isolates and all the selected isolates possessed the ITS gene. Phylogenetic and sequence analysis showed that A. niger, A. fumigatus, and C. albicans avian isolates are closely related to human fungal isolates including those causing respiratory affection and recently reported emerging azole-resistant fungi. However, A. flavus isolates were related to toxic aflatoxins producing fungi. The current study concluded that cinnamon and thyme EOs had strong antifungal activity indicating their potential usefulness for antifungal preparations. Moreover, the ITS gene sequencing is a robust technique for the identification of fungi on the species and relatively on the strain levels.