Virulence and resistance factors of pathogenic Candida species

There has been a recent increase in local and systemic infections due to pathogenic fungi. The yeast Candida albicans is the most important fungal pathogen, causing superficial (e.g. oral thrush) as well as disseminated infections. Several characteristics of C. albicans are discussed as putative virulence factors. The colonization of the host organism is mediated by a variety of specific adherence factors. Another virulence factor which can be correlated with the pathogenicity of C. albicans is the secretion of proteinases and phospholipases. The ability to undergo a morphological transition from the yeast to a hyphal growth form may also be important during infection. Another process which possibly plays a role in pathogenicity is the phenotypic switching, the ability to change cell surface properties like adhesion and antigenicity in a reversible manner, resulting in different colony morphologies. C. albicans infections can be treated with antifungal agents which are active against the fungal cytoplasmic membrane. While polyenes increase the permeability of fungal membranes by binding to membrane sterols, the members of the azole class of antimycotic drugs inhibit ergosterol biosynthesis. Other therapeutic agents interfere with nucleic acid biosynthesis. Clinically important resistances have been observed especially to azoles and nucleic acid base analogues.