The In Vitro Efficacy of Essential Oils and Antifungal Drugs Against Prototheca zopfii

The algae of the genus Prototheca are environmental pathogens whose main reservoir is the habitat of cows. They can cause protothecosis in domestic and wild animals, as well as human beings, with the main etiological agents being Prototheca zopfii in animals and Prototheca wickerhamii in humans. The aim of the study was to evaluate the in vitro activity of selected essential oils and antifungal antibiotics against P. zopfii isolates. The material consisted of nine P. zopfii strains isolated from the milk of cows suffering from mastitis. Eight essential oils produced by POLLENA-AROMA, Poland, and nine antifungal agents were tested. The effects of essential oils on P. zopfii were evaluated by microdilution with liquid Sabouraud dextrose broth, and susceptibility to antifungal agents was tested using the disk-diffusion method. All used essential oils inhibited the activity of P. zopfii isolates, with MIC values ranging from 0.2 to 10.5 mu l/ml. Cinnamon, clove, and thyme demonstrated the highest activity against the tested P. zopfii strains at concentrations ranging from 0.6 to 1.0 mu l/ml. Of the antifungal agents, the tested strains were the most sensitive to nystatin (100 %). The tested essential oils can be used to complement protothecosis therapy in animals and human beings.