Caspofungin affects adhesion of Candida to a human cell line

Cell wall composition and biofilm formation of azoles-susceptible and -resistant Candida glabrata strains

In the present study, three strains of Candida glabrata have been investigated to shed light on the mechanisms involved in azole resistance during adherence and biofilm formation. In particular, a clinical isolate, susceptible to azole-based drugs, DSY562 and two different resistant mutagenic strains deriving from DSY562, SFY114 and SFY115, have been analysed with different approaches for their cell wall composition and properties. A proteomic analysis revealed that the expression of six cell wall-related proteins and biofilm formation varied between the strains. The SFY114 and SFY115 strains resulted to be less hydrophobic than the susceptible parental counterpart DSY562, on the other hand they showed a higher amount in total cell wall polysaccharides fraction in the total cell wall. Accordingly to the results obtained from the hydrophobicity and adherence assays, in the resistant strain SFY115 the biofilm formation decreased compared to the parental strain DSY562. Finally, the total glucose amount in resistant SFY115 was about halved in comparison to other strains. Taken together all these data suggest that azole drugs may affect the cell wall composition of C. glabrata, in relation to the different pathogenic behaviours.

Characterization of biofilms in drug-sensitive and drug-resistant strains of Candida albicans

In this study, we investigated the biofilm formation in strains of Candida albicans susceptible (CO23) or resistant to fluconazole (CO23RFLC) or micafungin (CO23RFK). The effect of drug resistance on biofilm formation was investigated through the cell surface hydrophobicity and the mannan content. Moreover, biofilm formation was evaluated after 24, 48 and 72 hours with crystal violet assay, dry weight, as well as scanning electron microscopy. Our results showed an increase in hydrophobicity, polysaccharides content, metabolic activity and dry weight. Observation of sensitive and resistant strains confirmed the differences in cell morphology. Finally, the expression of genes involved in biofilm formation, such as HWP1 and EFG1, evaluated with relative real-time RT-PCR. Resistant strains proved to up- regulate the expression of HWP1. These results demonstrated the existence of important differences between drug-susceptible and drug-resistant strains biofilm of C. albicans.

Adherence of Candida albicans and Candida parapsilosis to epithelial cells correlates with fungal cell surface carbohydrates

Many studies have described the adherence of Candida albicans to epithelial cells but little is known about Candida parapsilosis adhesion and its role in host cell surface recognition. This study was designed to evaluate the correlation between the adherence of 20 C. albicans and 12 C. parapsilosis strains to human buccal epithelial cells and the expression of fungal cell surface carbohydrates using lectin histochemistry. Adherence assays were carried out by incubating epithelial cells in yeast suspensions (10(7) cells ml(-1) ) and peroxidase conjugated lectins (Con A, WGA, UEA I and PNA at 25 μg ml(-1) ) were used for lectin histochemistry. The results showed that adherence was overall greater for C. albicans than for C. parapsilosis (P < 0.01) and that the individual strain differences correlated with a high content of cell surface α-l-fucose residues as indicated by the UEA I staining pattern. Based on the saccharide specificity of the lectins used, these results suggest that l-fucose residues on cell surface glycoconjugates may represent recognition molecules for interactions between the yeast strain studied and the host (r = 0.6985, P = 0.0045). In addition, our results indicated the presence of α-d-glucose/α-d-mannose, N-acetyl-D-glucosamine/N-acetylneuraminic acid and D-galactose/N-acetyl-D-galactosamine in fungal cell wall.

Candida albicans metabolite affects the cytoskeleton and phagocytic activity of murine macrophages

Candida albicans is the most common opportunistic fungal pathogen of humans, causing systemic disease in immunocompromised patients. Host resistance to C. albicans infections is mediated predominantly by neutrophils and monocytes/macrophages. We have previously shown that exposure of a human epithelial cell line (HEp2) to C. albicans or to a culture filtrate of C. albicans caused actin rearrangement in the HEp2 cells. Since shifting of actin from the filamentous to the globular form may be crucial to the activity of phagocytes, we assessed in the present study the effect of the C. albicans metabolite (lyophilized culture filtrate) on the cytoskeleton of murine peritoneal macrophages and on their phagocytic activity. Our results showed a significant decrease in phagocytosis of C. albicans, ranging from 53-63% and a 25% reduction for C. glabrata cells. Using confocal laser scanning microscopy an actin rearrangement in the macrophages could be demonstrated that may be associated with the decrease of phagocytosis. We also tested the effect of mannan and of the secreted aspartic proteinase (Sap) inhibitor--pepstatin, on the activity of the metabolite in order to define the putative component and found no influence. In conclusion, our data indicate that a C. albicans metabolite affects phagocytic activity of macrophages, probably by alterations in their cytoskeleton.