PHENOTYPIC SWITCHING PROMOTES MODIFICATIONS IN CANDIDA TROPICALIS CAPABILITY ADHESION TO VERO CELLS

Candida tropicalis has been frequently associated with episodes of candidemia. The host adhesion by yeast cells are directly relate to cell wall composition, being determinant to the success of infection. Phenotypic switching promotes changes in colony macromorphology and cells morphology, and can modify the expression of some virulence traits. This study aimed to evaluate the effect of phenotypic switching on adhesion of C. tropicalis morphotypes to Vero cells. Thirteen morphotypes of three switching systems (49.07, 100.10 and 335.07) were evaluated: 3 parental (Clinical isolates) and 10 switched strains. Culture plates of Vero cells (ATCC, CLL-81), with 80% confluence in monolayer was co-cultured with C. tropicalis morphotypes (1x107cells/mL) and incubated for 2 hours at 37 °C in 5 % CO2, in DMEM medium. Next, the wells were washed with PBS and colored with crystal violet (1%). Ethanol:acetone solution was added to remove color from epithelial cells, and absorbance was measure in 570 nm, for total biomass quantification. The median of yeasts adhered to Vero cells was also evaluated. Cells were adhered in glass coverslips, and co-cultivation was conducted as described above. Cells were fixed with paraformaldehyde and staining by methylene blue (1%). Quantification of yeast distribution per Vero cell was made using an optical microscope. Adhesion of the greater part of switched strains (60%) differed from Parental adhesion. Of these, 50% were more adherent than Parental strains (Rough of 49.07; Crepe and Rough Revertants of 100.10), and for the others 50% the adhesion was lower than Parental (Crepe of 49.07 and 100.10 system; Irregular center to 335.07). The median of distribution of yeast adhered to Vero cells differed for 40% of the switching strains compared to Parental. Of these, 25% was more adherent (Crepe Revertant of 49.07) and 75% was lower adherent than Parental (Rough of 49.07; Crepe and Rough of 100.10). Our results, showed high correlation between the means of yeast cells distribution per Vero cell and total biomass, by Pearson correlation coefficient (r = 0.7). Of note, the median of yeast of the Parental adhered per Vero cell was similar the observed for Revertants strains. Besides, for all Revertants evaluated, 80% showed higher median of yeast adhered per Vero, than their counterpart variants (Crepe and Rough Revertants-49.07; Crepe Revertants 100.10; Irregular center revertant of 335.07). Our results showed that phenotypic switching changes adhesion profile of C. tropicalis to Vero cells, and that colony complexity is not relate to adhesion.