In vitro virulence determinants, comparative pathogenicity of clinical isolates and literature review of the D. rugosa complex.

Opportunistic mycoses by yeasts have increased considerably in the last three decades. Although is considered one of the most important causes of nosocomial infections, there is a recent shift to non- species as the most frequently isolated yeasts in particular risk groups. (formerly ) is a complex that includes four species: sensu stricto, , and , and they are estimated to represent 0.2% of all clinical isolates. In this study, we analyze nine clinical isolates of with focus on the virulence determinants and pathogenicity of the species by means of a survival model. Overall, we detected very strong aspartyl-protease and esterase activities. In contrast, both DNase and hemolysin activities were evident in only two of the isolates. None of the isolates was positive for phospholipase activity. All isolates studied were able to form biofilm after 72 h of incubation in a robust manner when compared with the strain used as control. Susceptibility testing showed minimum inhibitory concentrations (MICs) ≤1 µg/mL for amphotericin B in all isolates tested. Eight out of nine of the isolates had MICs ≤2 µg/mL for fluconazole. All isolates were resistant to both anidulafungin and caspofungin (MICs ≥1 µg/mL). We found a significant difference ( < 0.0001) amongst the survival curves for the different isolates in the survival model. Strains HPM309 and H259 produced an acute infection and exhibited the highest virulence, whereas the isolates 99-480 and DM17 proved to be the less virulent strains.