Candida albicans Clinical Isolates from a Southwest Brazilian Tertiary Hospital Exhibit MFS-mediated Azole Resistance Profile.

Ana Carolina C Pinto,Maria L Junqueira,Antonio Ferreira-Pereira,Daniel C De Moraes,Debora A.S Rocha

doi:10.1590/0001-3765201920180654

Abstract

Candida albicans is the most frequent fungal species that causes infections in humans. Fluconazole is the main antifungal used to treat Candida infections, and its prolonged and indiscriminate use for the last decades are the most established causes which originated resistant strains. Fungal drug resistance is associated to alterations in ERG11 gene and overexpression of multidrug resistance (MDR) transporters belonging to two families: ATP-binding cassette (ABC) and Major Facilitator Superfamily (MFS). To evaluate the role of MFS transporters in azoles resistance of C. albicans clinical strains, this study aimed to analyze four Candida albicans clinical isolates from the University Hospital in Juiz de Fora (Minas Gerais/Brazil), selected in our previous study as they were unaffected by FK506, an ABC pumps inhibitor. In a primary investigation on MFS proteins overexpression, the extrusion of fluorescent substrates (rhodamine 6G and nile red) was analyzed by fluorescence microscopy and flow cytometry. Results suggest participation of MFS transporters in azole resistance of C. albicans isolates and indicate the existence of secondary resistance mechanisms. Therefore, this study contributes to the information about Candida albicans infections in Brazil and reinforces the importance of epidemiological studies focusing on an improved understanding of the disease and further resistance reversion.

Highlights

Candida species are commensal organisms in healthy individuals
The identification of the MDR transporters - ATP binding cassette (ABC) proteins (Kaur and Bachhawat 1999) and the membrane proteins belonging to the major facilitator superfamily (MFS) (Fling et al 1991) - was soon considered as important as ERG11 modifications on multidrug resistance phenotype (Cannon et al 2009)
In a previous study (Neves-Junior et al 2015), we demonstrated through a chemosensitization assay, using FK506, that fluconazole resistance of seven out of 93 Candida strains was not mediated by ATP-binding cassette (ABC) transporters

Summary

Introduction

Candida species are commensal organisms in healthy individuals. in immunocompromised patients, they may cause a disease called candidiasis, which vary from harmless superficial mycosis to highly life-threatening systemic infections (MorioBIOLOGICAL SCIENCESAn Acad Bras Cienc (2019) 91(3)AZOLE RESISTANCE MEDIATED BY MFS TRANSPORTERSThe antifungal activity of azoles relies on the inhibition of lanosterol 14α-demethylase (ERG11), a key enzyme in ergosterol biosynthesis. The mechanisms of azole resistance of Candida species are well established, including overexpression or mutations in ERG11 (Sanglard et al 1998); changes in the ergosterol biosynthesis pathway, and energydependent drug efflux (Sanglard et al 1995). The identification of the MDR transporters - ATP binding cassette (ABC) proteins (Kaur and Bachhawat 1999) and the membrane proteins belonging to the major facilitator superfamily (MFS) (Fling et al 1991) - was soon considered as important as ERG11 modifications on multidrug resistance phenotype (Cannon et al 2009). MDR1, the major MFS transporter gene related to drug resistance (White 1997), was primarily identified in 1991, in transformed Saccharomyces cerevisiae strains and later, linked to azole resistance in C. albicans (White et al 1998)

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