Candida albicans signalling alcohols as players of cellular cross-talk with Candida tropicalis

Abstract number: O215

Martins M., Henriques M., Azeredo J., Oliveira R.

Objective:Candida species are the most common agents of opportunistic mycoses, which are often associated with biofilms. Candida albicans and Candida tropicalis biofilms develop most frequently in intracardiac prosthetic devices and voice prostheses with an infection risk of 1–3% and 50–100%, respectively. In natural environments polymicrobial biofilms are observed, but interactions between organisms are not well understood. This study focused on the evaluation of the effect of recently characterised C. albicans alcohols signalling molecules, in C. tropicalis regarding two hypothetical clinical scenarios: C. tropicalis, adhered and within a mature biofilm.

Methods: All experiments were performed in RPMI medium and cells (initial cell density of 1×10⁶ cells/ml) grown at 37°C, 130 rpm. For all experiments, endpoints were determined at the end of 24 h. C. tropicalis ATCC 750 biofilms were developed on the surface of microtriter plates. C. albicans CECT 1472 secreted alcohols were added after 3 h of adhesion or to 48 h grown biofilms. Isoamylalcohol, 2-phenylethanol, 1-dodecanol, nerolidol, farnesol and tyrosol were independently assayed at physiological levels. Biofilm quantification was performed using two different approaches: total biomass by crystal violet staining and quantification of biofilm cells activity by the reduction of a tetrazolium salt (XTT).

Results: At initial biofilm stages C. tropicalis metabolic cell activity was significantly decreased by isoamylalcohol, 2-phenylethanol, E-nerolidol and tyrosol treatments, while cellular mass was positively affected by isoamylalcohol but negatively by E-nerolidol. Nevertheless, mature biofilms were more resistant to the action of these alcohols. Specifically, only isoamylalcohol induced alterations, with the same response pattern observed at earlier stages.

Conclusion: Results obtained show that C. albicans extracellular alcohols regulate C. tropicalis behaviour, depending on biofilm growth time, suggesting that C. tropicalis mature biofilms are more resistance to C. albicans signalling crosstalk.