In vitro and in vivo Effect of Exogenous Farnesol Exposure Against Candida auris

Fruzsina Nagy; Eszter Vitális; Ágnes Jakab; Andrew M Borman; Lajos Forgács; Zoltán Tóth; László Majoros; Renátó Kovács

doi:10.3389/fmicb.2020.00957

In vitro and in vivo Effect of Exogenous Farnesol Exposure Against Candida auris

Front Microbiol. 2020 May 20:11:957. doi: 10.3389/fmicb.2020.00957. eCollection 2020.

Authors

Fruzsina Nagy^{1

2}, Eszter Vitális^{2

3}, Ágnes Jakab⁴, Andrew M Borman⁵, Lajos Forgács^{1

2}, Zoltán Tóth^{1

2}, László Majoros¹, Renátó Kovács^{1

6}

Affiliations

¹ Department of Medical Microbiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
² Doctoral School of Pharmaceutical Sciences, University of Debrecen, Debrecen, Hungary.
³ Hospital Hygiene Ward, Clinical Centre, University of Debrecen, Debrecen, Hungary.
⁴ Department of Molecular Biotechnology and Microbiology, Faculty of Science and Technology, Institute of Biotechnology, University of Debrecen, Debrecen, Hungary.
⁵ UK National Mycology Reference Laboratory, Public Health England, Bristol, United Kingdom.
⁶ Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary.

Abstract

The spreading of multidrug-resistant Candida auris is considered as an emerging global health threat. The number of effective therapeutic regimens is strongly limited; therefore, development of novel strategies is needed. Farnesol is a quorum-sensing molecule with a potential antifungal and/or adjuvant effect; it may be a promising candidate in alternative treatment against Candida species including C. auris. To examine the effect of farnesol on C. auris, we performed experiments focusing on growth, biofilm production ability, production of enzymes related to oxidative stress, triazole susceptibility and virulence. Concentrations ranging from 100 to 300 μM farnesol caused a significant growth inhibition against C. auris planktonic cells for 24 h (p < 0.01-0.05). Farnesol treatment showed a concentration dependent inhibition in terms of biofilm forming ability of C. auris; however, it did not inhibit significantly the biofilm development at 24 h. Nevertheless, the metabolic activity of adhered farnesol pre-exposed cells (75 μM) was significantly diminished at 24 h depending on farnesol treatment during biofilm formation (p < 0.001-0.05). Moreover, 300 μM farnesol exerted a marked decrease in metabolic activity against one-day-old biofilms between 2 and 24 h (p < 0.001). Farnesol increased the production of reactive species remarkably, as revealed by 2',7'-dichlorofluorescein (DCF) assay {3.96 ± 0.89 [nmol DCF (OD₆₄₀)^-1] and 23.54 ± 4.51 [nmol DCF (OD₆₄₀)^-1] for untreated cells and farnesol exposed cells, respectively; p < 0.001}. This was in line with increased superoxide dismutase level {85.69 ± 5.42 [munit (mg protein)^-1] and 170.11 ± 17.37 [munit (mg protein)^-1] for untreated cells and farnesol exposed cells, respectively; p < 0.001}, but the catalase level remained statistically comparable between treated and untreated cells (p > 0.05). Concerning virulence-related enzymes, exposure to 75 μM farnesol did not influence phospholipase or aspartic proteinase activity (p > 0.05). The interaction between fluconazole, itraconazole, voriconazole, posaconazole, isavuconazole and farnesol showed clear synergism (FICI ranges from 0.038 to 0.375) against one-day-old biofilms. Regarding in vivo experiments, daily 75 μM farnesol treatment decreased the fungal burden in an immunocompromised murine model of disseminated candidiasis, especially in case of inocula pre-exposed to farnesol (p < 0.01). In summary, farnesol shows a promising therapeutic or adjuvant potential in traditional or alternative therapies such as catheter lock therapy.

Keywords: biofilm; in vivo; oxidative stress; quorum-sensing; synergy; therapy; triazoles; virulence.