Candida tropicalis affects the virulence profile of Candida albicans: an in vitro and in vivo study.

Candida albicans and Candida tropicalis are commensal microorganisms occurring in the oral cavity of approximately 50%-70% of healthy individuals. However, these microbes can become pathogenic through changes in the environment or weakened host immune system. Thus, the aim of this investigation was to evaluate the interaction between species of the genus Candida in the biofilm formation, filamentation, gene expression and virulence in Galleria mellonella. Coincubation of C. albicans with C. tropicalis cells after 48 h resulted in significant reduction of biofilm formation by decreasing viable cell counts, metabolic activity and hyphal growth. The C. albicans genes (BCR1, CPH1, EFG1, UME6, HWP1, ALS3, SAP5 and PLB2) were quantified by quantitative real-time polymerase chain reaction and most of genes were downregulated. Regarding in vivo assay, the groups that the larvae received C. albicans and C. tropicalis had a significant survival increase compared to the control group of C. albicans (P = 0.0001) in agreement with the in vitro results. In conclusion, C. tropicalis colonization was associated with a decrease in the growth of C. albicans, suggesting an antagonistic relation between these two species. Therefore, C. tropicalis by reducing C. albicans virulence profile may limit the ability of this pathogenic fungus to cause infection.