Hematogenic candidiasis: a multidisciplinary approach for the improvement of diagnostic tools and caracterization of biomarkers related to its prognosis

Abstract

Haematogenic infections caused by Candida albicans in hospitalized patients are of great impact in worldwide public health in terms of morbidity and mortality. Recent progress on the development of antifungal drugs has not reduced the lethality of candidaemia which is still approximately 40 to 50% of infected patients. The objectives of this project are therefore (1) to improve diagnostic tools for haematogenic candidiasis using large scale analysis of rDNA internal transcribed spacer (ITS) as a rapid and accurate identification method for emerging species of Candida spp, (2) to develop molecular typing methods using mitocondrial DNA hypervariable regions for the identication of Candida spp outbreaks, (3) to contribute the understanding of host- pathogen interactions during the onset of haemopathogenic infection by C. albicans and (4) to characterize mutations in "Toll like" receptors (TLRs) and other pattern recognition receptors (PRRs) that recognize fungal glucans in patients with different clinical manifestations. To address objective (1) we will sequence intergenic spacers (IGS) and ITS of rDNA of C. albicans, C. dubliniensis, C. glabrata, C. parapsilosis, C. orthopsilosis, C. metapsilosis, etc. These sequences will be compared with other database sequences for identification. These results will be used to establish a gold standard method for rapid species identification of clinical isolates. The identification using molecular methods is mandatory to resolve inconsistencies arising from conventional methods in the identification of emerging yeasts such as C. dubliniensis, C. orthopsilosis and C. metapsilosis. For objective (2) we propose to use comparative genomics of mitocondrial DNA for typing and for objective (3) we plan to characterize virulence factors in fungal samples isolated from patients with different clinical outcomes. We are going to analyse the following virulence factors: adhesion to epithelial cells, morphogenesis, aspartyl proteinases (Saps) and phospholipase secretion and interaction with neutrophils. For objective (4) we plan to study the correlation of human PRRs, genetic diversity and host susceptibility to Candida spp. infection. The haplotypes of PRRs such as dectin 1 and Toll like receptor 2 will be sequenced from phagocitic cells obtained from blood samples of candidaemic patients routinely assisted by our group of clinicians encharged of blood stream infections patients care. (AU)