Author(s):
Rodrigues, Célia 
; Silva, Sónia Carina ; Azeredo, Joana ; Gonçalves, Bruna ; Henriques, Mariana
Date: 2013
Persistent ID: http://hdl.handle.net/1822/28488
Origin: RepositóriUM - Universidade do Minho
Subject(s): Candida glabrata biofilm resistance to antifungals ERG genes
Description
The occurrence of fungal infections has been significantly increasing, thus
contributing to higher morbidity and mortality. The use of broad-spectrum antibiotics,
catheters, immunosuppression diseases, chemo and radiotherapy are predisposing
factors for invasive fungal infection development. Candida albicans is the predominant
species in both health and disease conditions, yet, in the last two decades the number
of infections due to non-Candida albicans Candida species has increased significantly.
Once believed as non-pathogenic, Candida glabrata rapidly was perceived to be
responsible for many human diseases. Despite lacking a number of virulence factors
allied to the majority of Candida pathogenicity, C. glabrata possesses high ability to
colonize medical devices and human epithelium, resulting generally in biofilms
formation ability. Its intrinsically low susceptibility to azoles, such as triazoles (e.g.
fluconazole (Flu), voriconazole (Vcz)) and its biofilms tolerance is another problem.
The aim of this study was to evaluate the effects of Flu (largely used) and Vcz (hospitalenvironment
exclusive) in the control of C. glabrata biofilms and its relation with the
expression of genes encoding for Ergosterol: ERG3, ERG6 and ERG11. Three isolates of
C. glabrata (vaginal, urine and reference strain) were used. The Minimum Inhibitory
Concentration was determined for planktonic cells and biofilms were formed during 24h
and treated (for 24h) with different concentrations of both antifungal agents. The
effects of Flu and Vcz were analyzed by Colony Forming Units determination and by total
biomass quantification using Crystal Violet staining. Biofilms were also analyzed by
scanning electron microscopy. Total proteins and carbohydrates were quantified from
biofilms’ matrices. Moreover, ergosterol present in the matrices was also quantified by
HPLC. To end, qRT-PCR was used to study the gene expression of selected ERG genes.
Our results show that, unlike Flu, Vcz had a very good Candida biofilm eradication
capacity. No fluctuations between the two azoles were noticed in terms of proteins and
carbohydrates, both presenting a blocked production in the first and an overmetabolism
in the second. A new finding was the detection of ergosterol in the matrices.
The gene expression study showed overexpression of ERG genes, in the presence of the
both drug compounds. This work reveals the extraordinary capacity of C. glabrata to
change with the purpose of overcome the adversities of the environment. The increase
in ergosterol present in matrices and the overexpression of Erg genes could be an
explanation for higher C. glabrata biofilms tolerance. This aptitude makes hampered the
action of drugs against the cells, and when passing to the progeny, is, undoubtedly, a
great advantage to the development of resistance to antifungals, in Candida species.
