Year: 2013
Type: dissertation
Abstract: Candida bracarensis is a rare Candida species, which was recently discovered during an epidemiological study of candidiasis performed in Portugal. Initially, C. bracarensis was identified as C. glabrata, but detailed analyses showed differences between both species. However, there is still little information about C. bracarensis and, for that reason, this dissertation had the general aim to study three strains of the that species (NCYC 3133, CNM-CL-7030 and 153 MT) mainly in terms of its virulence factors and to compare them with C. glabrata ATCC 2001 and C. albicans ATCC 90028. The first objective was to characterize the three strains of C. bracarensis, concerning its colony and cell morphology and its growth kinetics. The results showed that, on CHROMagar, all strains presented white colonies, unlike C. albicans and C. glabrata. It was also verified that C. bracarensis species formed elliptic or oval cells, with an intermediate size comparatively to the other studied species, and that were unable to produce hyphae or pseudohyphae. In the growth kinetics, all species presented similar behaviours between them, but different specific growth rates. In addition to filamentous structures, other virulence factors of C. bracarensis were studied. The ability of each strain to adhere and form biofilms was assessed and, in this sequence, it was showed that C. bracarensis adhered in higher extension, in RPMI, and that its biofilms presented the lowest total biomass values. Additionally, the biofilm matrix composition was analysed, but few differences were detected between the studied species. Hydrolytic enzymes secretion was also assessed by growing the Candida strains on agar medium supplemented with BSA (proteases), egg (phospholipases) or blood sheep (haemolysins). C. bracarensis NCYC 3133 was able to secrete proteases, like C. albicans, but unlike C. glabrata. In addition, all C. bracarensis strains were able to produce haemolysins, but not phospholipases. Lastly, the antifungal resistance of C. bracarensis in planktonic cells and in biofilms (pre-formed and during its formation) was analysed. In both situations, strains NCYC 3133 and 153 MT were the most and least resistant species to amphotericin B, respectively. In contrast, all C. bracarensis strains showed high susceptibility to fluconazole, mainly in terms of planktonic cells. The effect of these antifungal agents in the enzymatic activity of C. bracarensis was also evaluated. Both agents caused a significant increase in the proteolytic activity, but in different Candida species. In conclusion, this study clarified some significant differences between C. bracarensis and C. glabrata, which were initially mistakenly, particularly concerning differences found in virulence traits and antifungal resistance.
Author: António André de Sousa Moreira
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2268603253