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Construction d'une souche de Candida lusitaniae génétiquement modifiée pour l'étude des mutations de résistance aux échinocandines caractérisées chez des isolats cliniques

Year: 2016
Type: dissertation
Abstract: Invasive fungal infection caused by Candida species are constantly growing over the last 20 years and are associated with high mortality rate. Prompt and accurate diagnosis is essential to initiate appropriate antifungal therapy. Because of the lack of sensitivity of blood cultures and their long delay of positivity, antifungals are often started without evidence of disease. Echinocandin drugs are widely used as empirical therapy of invasive candidiasis. Echinocandins target the fungal cell wall by blocking β-1,3-D-glucan synthase. In recent years, clinical failures due to the acquisition of point mutations in the FKS gene (encoding subunit of β-(1,3)-D-glucan synthase) have been reported. Most of the mutations occur in highly conserved regions called “hot spots” (HS). In Bordeaux Hospital University Center, over a 26-month period, 9 clinical isolates with FKS mutations have been identified. These resistant isolates have been charac terized by phenotypic and genotypic analysis. The high size of the FKS1 gene (around 5,5 kb) limits the analysis of its expression. Therefore, most studies only focused on the HS regions, using Saccharomyces cerevisiae as model. We developed a new model in Candida lusitaniae (a CTG-clade Candida species) for the homologous expression of full-length mutated FKS1 alleles. We characterized 3 mutations in the HS regions and studied the effect of the combination of 2 mutations on the resistance profile. The yeast model described in this work could be used to investigate the impact of FKS mutations in the interactions between Candida spp and phagocytes, with or without echinocandin.
Source: HAL
Language: French
Field: Medicine
Open Access status: green
OpenAlex ID: W2733658471
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