Effect of fatty acids on biofilm formation, oxidative stress and antifungal susceptibility of Candida albicans and Candida dubliniensis

Abstract

English: Candida albicans and C. dubliniensis are commensals of the gastrointestinal and genitourinary tract in healthy individuals. However, in diseased individuals they can cause superficial infections to deep seated mycoses. Both species form mycelial networks called biofilms, and formation of biofilms results in increased resistance towards antifungal compounds currently in use. Therefore, there is a need for alternative antifungal compounds such as fatty acids. Research has shown that supplementation of growth medium with polyunsaturated fatty acids (PUFAs), increased the unsaturation index and made cells susceptible to lipid peroxidation and cell death. During this study this phenomenon was evaluated on biofilms of C. albicans and C. dubliniensis using selected PUFAs. Due to differences in the carbon chain length and saturation of fatty acids, they interact differently with the cell membrane and will have different peroxidisability values. The results from the study showed C18:4 n-3 and C20:5 n-3 were taken in by the cell and resulted in increased unsaturation index. The results further indicated oxidative stress-induced apoptosis following supplementation with C18:4 n-3 and C20:5 n-3 in biofilms of both C. albicans and C. dubliniensis. The induction of apoptosis following supplementation by C18:4 n-3 and C20:5 n-3 was confirmed by mitochondrial membrane potential assay, Annexin V-FITC staining, TUNEL assay and DAPI staining. The use of C18:4 n-3 in synergism with amphotericin B resulted in decreased dosage of the antifungal compound needed to inhibit biofilms of C. albicans and C. dubliniensis.

Afrikaans: Candida albicans en C. dubliniensis is kommensale van die gastro-intestinale en genitor-urinêre weg van gesonde individue. In siek individue kan hulle egter oppervlakkige tot sistemiese mikoses veroorsaak. Beide spesies vorm misiliêre netwerke wat biofilms genome word, en biofilmvorming veroorsaak verhoogde weerstand teen antifungale middels wat tans in gebruik is. Dus is daar ‘n behoefte aan alternatiewe antifungale middels soos vetsure. Navorsing het getoon dat byvoeging van polionversadigde vetsure (PUFAs) tot groeimedia, die onversadigingsindeks verhoog en selle vatbaar maak vir lipiedperoksidasie en dood. Hierdie verskynsel is gedurende hierdie studie geëvalueer op biofilms van C. albicans en C. dubliniensis met sekere PUFAs. As gevolg van die verskille in koolstofkettinglengte en versadiging van vetsure verskil die interaksies wat hulle met selmembrane het en sal hulle verskillende vlakke van peroksideerbaarheid hê. Die resultate van hierdie studie het aangetoon dat C18:4 n-3 en C20:5 n-3 deur die selle opgeneem is en ‘n toename in onversadigingsindeks veroorsaak het. Verder het die reulate getoon dat behandeling van beide C. albicans en C. dubliniensis biofilms met C18:4 n-3 en C20:5 n-3 gelei het tot oksidatiewe stress veroorsaakde apoptose. Die induksie van apoptose na behandeling met C18:4 n-3 en C20:5 n-3 is bevestig met ‘n mitochondriale membraanpotensiaaltoets, Annexin V-FITC kleuring, TUNEL toets en DAPI kleuring. Die gebruik van C18:4 n-3 in sinergisme met amfoterisien B het gelei tot ‘n verlaagde dosis van die antifungale middel wat nodig was om biofilms van C. albicans en C. dubliniensis te inhibeer.