Antifungal activity of plant essential oils against wild strains of Candida spp. isolated from hospitalized patients

Abstract

The antimicrobial activity of Basil oil, Chamomile Blue oil, Origanum oil, Tea Tree oil and Thyme oil was investigated using a broth macrodilution method against 12 strains of Candida spp isolated from clinical specimens (wounds, blood and urine), derived from various patients entering the University Hospital of Ioannina plus one ATCC Candida strain. The strains used in this study were C. albicans (n=4), C. parapsilosis (n=5), C. tropicalis (n=2), C. glabrata (n=1) and C. albicans ATCC 10231. Susceptibility test to antimicrobials was performed using the Bauer-Kirby method and the Vitek II system (Biomerieux). Basil oil (W211907), Chamomile Blue oil (W227307), Origanum oil (W282812), Tea Tree oil (W390208) and Thyme oil (W306509) were obtained from Sigma-Aldrich (Germany). Carvacrol and thymol (Origanum oil), thymol, linalool and p-cymene (Thyme oil), terpine-4-ol and p-cymene (Tea tree oil), methyl chavicol (Basil oil) were the main components of the tested oils. The antifungal activity of the selected essential oils was tested also by the viable counts method and the optical density method in addition to the broth macrodilution method and the Minimal Inhibition Concentration (MIC) was determined at 24 hours, 48 hours and 7 days. All experiments were performed in duplicate. All tested essential oils except the Chamomile Blue oil, displayed similar antifungal activity ranging from 0.06 to 0.37% (v/v). Specifically, the MIC values for Origanum oil ranged from 0.06 to 0.25% (v/v), for Basil oil from 0.06 to 0.37% (v/v), for Tea Tree oil from 0.09 to 0.25% (v/v) and for Thyme oil from 0.12 to 0.25% (v/v), while Chamomile Blue oil exhibited no antifungal properties. After the 7th day of incubation the MIC values for the tested oils except Chamomile Blue oil, ranged from 0.12 to 0.5% (v/v). Relevant studies by other researchers report MIC values ranging from 0.04 to 0.12% (v/v) for origanum oil, 0.12 to 0.32% (v/v) for thyme oil, 0.18 to 0.5% (v/v) for basil oil and 0.03 to1% (v/v) for tea tree oil, while there are no data available for chamomile blue oil.