Efecto de la frecuencia de irradiación de antraquinonas en la fotoinactivación de Candida tropicalis biofilms.

JULIANA, MARIONI; LAURA R. COMINI; JOSÉ L. CABRERA; MARÍA G. PARAJE; SUSANA C. NÚÑEZ MONTOYA.

Córdoba

Jornada; . III Reunión de Fotobiólogos Moleculares.; 2017

Background: Candidatropicalis is increasingly becoming among the most commonly isolatedpathogens causing fungal infections with an important biofilm-forming capacity.Purpose: This study addresses the antifungal effect ofrubiadin (AQ1) and rubiadin 1-methylether (AQ2), two photosensitizing anthraquinones (AQs) isolated from Heterophyllaea pustulata, against C. tropicalis biofilms, by studying the cellular stress and antioxidant response intwo experimental conditions: darkness and irradiation. The combination with Amphotericin B (AmB) wasassayed to evaluate the synergic effect.Study Design/Methods: Biofilms of clinical isolatesand reference strainof Candidatropicalis were treated with AQs (AQ1 or AQ2) and/or AmB, and the biofilms depletion was studied by crystal violet and confocal scanning lasermicroscopy (CSLM). The oxidant metabolites productionand the response of antioxidant defense system were also evaluated under dark and irradiation conditions,being the light a trigger for photo-activation of the AQs. The Reactive Oxygen Species(ROS) were detected by the reduction of Nitro Blue Tetrazolium test, and ReactiveNitrogen Intermediates (RNI) by the Griess assay. ROSaccumulation was also detected inside biofilms by using2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) probe, which wasvisualized by CSLM. Superoxidedismutase (SOD) activity and the total antioxidant capacity of biofilms were measured byspectrophotometric methods. The minimun inhibitory concentration for sessile cells (SMIC) was determined for eachAQs and AmB. The fractional inhibitory concentration index (FICI) was calculatedfor the combinations of each AQ with AmB by the checkerboard microdilutionmethod.Results: Biofilm reduction of both strains was more effective with AQ1 than with AQ2. The antifungaleffect was mediated by anoxidative and nitrosative stress under irradiation, with a significant accumulationof endogenous ROS detected by CSLM and an increase in the SOD activity. Thus,the prooxidant-antioxidant balance was altered especially by AQ1. The bestsynergic combination with AmB was also obtained with AQ1 (80.5 %) (FICI = 0.74).Conclusion: Underirradiation, the oxidative stress was the predominant effect, altering the prooxidant-antioxidantbalance, which may be the cause of the irreversible cell injury in the biofilm. Our results showed synergismof these naturalAQs with AmB. Therefore, the photosensitizing AQ1 couldbe an alternative for the Candidainfections treatment, which deserves further investigation.