Contents lists available at ScienceDirect Industrial Crops & Products journal homepage: www.elsevier.com/locate/indcrop Combined effect of Thymus capitatus and Cinnamomum verum essential oils with conventional drugs against Candida albicans biofilm formation and elucidation of the molecular mechanism of action Rym Essid a , Dorra Gharbi a , Ghassen Abid b , Ines Karkouch a , Thouraya Ben Hamouda a , Nadia Fares a , Darine Trabelsi b , Haythem Mhadhbi b , Salem Elkahoui a , Ferid Limam a , Olfa Tabbene a, ⁎ a Laboratory of Bioactive Substances, Center of Biotechnology, Ecopark of Borj Cedria, Hammam-Lif, Tunisia b Laboratory of Legumes, Center of Biotechnology of Borj Cedria, University of Tunis El Manar, 901, 2050 Hammam-Lif, Tunisia ARTICLE INFO Keywords: Antibiofilm formation C. albicans Cinnamomum verum Thymus capitatus Gene expression Secreted aspartic protease ABSTRACT Biofilm formation by the pathogenic strain Candida albicans (C. albicans) is a crucial virulence factor on biotic and abiotic surfaces especially in medical devices. The present study investigated the effects of Cinnamomum verum and Thymus capitatus essential oils (EOs) and their combination with antifungal drugs on the development of biofilm and mature biofilm. The molecular mechanism of action was also investigated. Results showed that C. verum and T. capitatus EOs were broadly effective against C. albicans biofilm formation exhibiting 85.57% and 80.6% inhibition at half MIC values, respectively. Furthermore, they showed 92.79 and 94.46% eradication of C. albicans mature biofilm at 2xMIC values. Moreover, these EOs were able to reduce the production of secreted aspartic proteases by > 90% at 0.75xMIC. The antibiofilm potency was improved when EOs were combined with AMB, effectively eradicating C. albicans mature biofilm on central venous catheter (CVC). Transcriptomic ana- lyses indicated that EOs, especially when combined with AMB, down-regulate Ras-cAMP-Efg and MAPK sig- naling genes. In addition, EOs and their combination with AMB significantly inhibited the expression of adhesion and secreted aspartyl proteinase virulence factor genes. Our results demonstrated that C. verum and T. capitatus EOs and their combination with AMB could provide an effective treatment against C. albicans biofilm on medical devices. 1. Introduction Candida (C.) albicans is one of the main pathogens of candidiasis (Martins et al., 2014). Under certain conditions, C. albicans is able to switch from yeast to hypha form which is crucial for biofilm formation and pathogenicity, causing systemic life-threatening and invasive in- fections (Mayer et al., 2013). Yeast to hyphal form transition in C. al- bicans biofilm is under the control of numerous specific gene expression as part of complex signaling pathways involving several transcription factors (Rajasekharan et al., 2018), among which the Ras1p-cAMP- protein kinase A (PKA) and the mitogen-activated protein kinase (MAPK) pathways (Shareck and Belhumeur, 2011). Hyphal growth can be down-regulated by the interaction of Tup1p repressor with Nrg1p and Rfg1p DNA binding proteins (Theberge et al., 2013). These com- plex signaling pathways control filamentous growth via the regulation of agglutinin-like sequences (ALS) proteins and hyphal wall protein 1 (HWP1) involved in cell adhesion (Shareck and Belhumeur, 2011;). Besides, C. albicans can acquire virulence enabling the pathogenic strain to produce proteolytic enzymes including secreted aspartyl proteinases (SAPs) involved in promoting adhesion, invasion and damage of host tissues (Pietrella et al., 2010). Hyphal form is a crucial step for C. al- bicans virulence as it provoked the colonization of various tissues and the contamination of medical devices such as venous catheters, urinary catheters, heart valves, cardiac pacemakers, dental prosthesis and ar- tificial joints (Francolini and Donelli, 2010; Fais et al., 2017). Medical device related contaminations are difficult to treat as pathogenic cells are protected within the biofilm structure, and currently the best option is the complete removal of the catheter associated C. albicans (Rex et al., 2000). However, this option is uncomfortable and hazardous and could lead to organic damage in patients (Lewis et al., 2002). In severe Candida infections, the treatment of choice is based pri- marily on fluconazole and amphotericin B (AMB). The latter interfere https://doi.org/10.1016/j.indcrop.2019.111720 Received 31 May 2019; Received in revised form 29 July 2019; Accepted 23 August 2019 ⁎ Corresponding author. E-mail address: tabb_olfa@yahoo.fr (O. Tabbene). Industrial Crops & Products 140 (2019) 111720 Available online 30 August 2019 0926-6690/ © 2019 Published by Elsevier B.V. T