Objective: Aminocandin (AC) is a new member of the echinocandin class of antifungals that is undergoing development. The aim of this study was to assess the effect of AC on the morphology of Aspergillus fumigatus and Candida albicans using confocal scanning laser microscopy (CSLM) and scanning electron microscopy (SEM). Methods: For CSLM, A. fumigatus and C. albicans were grown in the presence of different concentrations of AC and stained with two specific fluorescent stains, FUN-1 TM (10 μM) and concanavalin A-Alexa fluor 488 conjugate (CONA; 25 μg/ml). FUN-1 is converted to orange-red cylindrical intravacuolar structures by metabolically active cells, while CONA binds with green fluorescence to glucose and mannose residues of fungal cell and hyphal wall polysaccharides, differentiating intact and damaged structures. To determine the structure of each cell, a series of horizontal (xy) optical sections were taken throughout the full length of the cell and hyphal forms, and images of red (FUN-1) and green (CONA) were conceived simultaneously using a multitrack mode. Isolates was prepared for SEM by a series of fixative and dehydration steps, sputter coated with Au/Pd (60/40), and viewed with an Amray 1000B scanning electron microscope. Results: Unlike untreated controls, A. fumigatus hyphal forms treated with AC (0.125 μg/ml) were lysed, with bulging ends and stunted growth. Treatment of C. albicans with AC (0.008 and 0.015 μg/ml) resulted in swelling of yeast cells and thinning of the cell wall. Increasing concentration (0.03 to 0.06 μg/ml) resulted in complete cell inhibition, with only remnants of cell walls seen. SEM confirmed the results obtained by CSLM for both isolates. Conclusion: Our data show that AC treatment alters the morphology of A. fumigatus and C. albicans consistent with the mode of action of echinocandins that inhibits the 1,3 beta-D-glucan synthase, leading to cell wall inhibition, collapse and eventual death.
Full conference title:
16th European Congress of Clinical Microbiology and Infectious Diseases
- ECCMID 16th (2006)