Virulence factor in Candida albicans infections and their clinical relevance

Abstract

Most of fungal infections are superficial and relatively easy to treat. Nevertheless, millions of invasive fungal infections have also been reported. Considering that most of the time the presence of this fungus represents colonization, the challenge is to differentiate between colonization and infection. The objective is to summarize the Candida spp. virulence factors and to highlight their clinical relevance. We have selected the most pertinent articles from the recent medical literature regarding this subject using Google Academic and Pubmed databases. The first virulence factors involved in the infection are adhesion proteins (e.g., the fungal protein gpm1 interacts with vibronectin, leading to fungal adhesion to keratinocytes, endothelial cells and monocytes). In order to invade, the fungus penetrates the epithelium/endothelium using hydrolytic enzymes - aspartyl proteases (encoded by SAP genes), phospholipases and lipases. Candida albicans could induce its own endocytosis by the epithelial cells, process governed by Efg1p and Tpk2p proteins. Penetration is favored by the yeast-hyphae conversion, pleomorphism being essential in pathogenicity. It is triggered by various factors including pH and temperature changes, hormonal variations etc. The fungus is very versatile, having the capacity to survive within a wide range of environmental conditions. It can cause co-infections with different bacteria such as Pseudomonas aeruginosa, Klebsiella pneumoniae etc. The virulence factor with the most important clinical significance is the capacity of biofilm formation. A significant role in biofilm formation is played by the adhesion proteins codified by ALS and EAP Candida albicans genes. Biofilm presence on medical instruments leads to antifungal resistance. The study of the Candida spp. virulence factors is a continually developing field. Understanding these mechanisms has a major clinical importance when comes to correct evaluation of a positive Candida spp. sample and correct treatment administration. It could also lead to new therapeutic approaches if we consider the increase of antifungal resistance in the last years. We highlight the importance of collaboration between the clinician and the laboratory physician.