Essential oil and plant extract of oregano as agents influencing the virulence factors of Candida albicans.

Candida albicans, a polymorphic yeast, is a physiological component of the human and animal commensal microbiome. It is an etiological factor of candidiasis, which is treated by azole antifungals. Growing resistance to azoles is a reason to look for other alternative treatment options. The pharmacotherapeutic use of plant extracts and essential oils has become increasingly important. In our experiment, C. albicans showed susceptibility to four observed plant extracts and essential oils from peppermint ( Mentha piperita), thyme ( Thymus vulgaris), sage ( Salvia officinalis), and oregano ( Origanum vulgare). Oregano plant extract and essential oil showed the highest antifungal activity, at MIC values of 4.9 mg/mL and 0.4 mg/mL respectively. Therefore, it was subjected to further research on the influence of virulence factors - biofilm formation, extracellular phospholipase production and germ tube formation. Oregano plant extract and essential oil showed an inhibitory effect on the observed C. albicans virulence factors at relatively low concentrations. The extract inhibited the adherence of cells at MIC 12.5 mg/mL and essential oil at MIC 0.25 mg/mL. Degradation of the formed biofilm was detected at MIC 14.1 mg/mL for plant extract and at MIC 0.4 mg/mL for essential oil. Extracellular phospholipase production was most effectively inhibited by the essential oil. In particular, the number of isolates with intensive extracellular phospholipase production decreased significantly. Of the 12 isolates intensively producing extracellular phospholipase, only 1 isolate (4.5%) retained intense production. Essential oil caused up to a 100 % reduction in germ tubes formation and plant extract reduced their formation depending on the concentration as follows: 2.6% (0.8 mg/mL), 21.2 % (6.25 mg/mL), and 64.5 % (12.5 mg/mL) compared to the control.

In vitro evaluation of zearalenone toxicity by comet assay.

The aim of this study was to reveal the potentially genotoxic effect of zearalenone on bovine lymphocytes by comet assay in vitro. The bovine lymphocytes were exposed to various zearalenone concetrations (50; 10; 2; 0.4 and 0.08 ppm). The viability and DNA damage of lymphocytes was monitored after 2 h, 24 h, 48 h and 72 h. After 2 hours of zearalenone exposure, statistically significant DNA damage occurred at all tested concentrations of 0.08 ppm (12.2±1.25; p⟨0.05), 0.4 ppm (12.7±0.88; p⟨0.01), 2 ppm (12.0±0.51; p⟨0.01), 10 ppm (11.2±0.47; p⟨0.01) and at 50 ppm (14.2±0 61; p⟨0.001). Significantly greater DNA damage was also found after 24 h, 48 h and 72 h. The obtained results showed that zearalenone may induce DNA damage of the bovine lymphocytes.

Efficacy of Lamiaceae essential oils with selected azoles against Candida albicans clinical isolates.

A current problem in candidiasis treatment is increasing resistance to azoles, which are often prescribed to patients. The study underlines the high resistance of yeasts to fluconazole, which achieved high MIC (minimal inhibitory concentration) values both alone and in combination with essential oils (EOs). Antifungal activity of Hyssopus officinalis, Thymus vulgaris, Salvia officinalis and Rosmarinus officinalis EOs was determined against 13 clinical isolates of Candida albicans and reference strain Candida albicans ATCC 10231. The synergistic effect was investigated for the combination of itraconazole and fluconazole with Hyssopus officinalis and Thymus vulgaris EOs. Based on the fractional inhibitory concentration index, the synergistic effect was achieved in all of the samples exposed to itraconazole with Hyssopus officinalis (FICI 0.3±0.06). On the other side, the additive effect was proven in use of itraconazole with Thymus vulgaris (FICI 0.75±0.35) and fluconazole with both EOs tested (FICI 0.81±0.19; 0.88±0.57) This study shows the importance of monitoring the synergistic effect of antifungals combined with EOs, because it is a possible solution for reducing the resistance and improving the disease prognosis.