The Ralationship Between Penicillium Marneffei Melanin and L-dopa
|School||Guangxi Medical University|
|Course||Dermatology and Venereology|
|Keywords||Penicillium marneffei melanin L-DOPA antifungal drugs susceptibility test in vitro|
Objective Explore the possible sources of Penicillium marneffei (PM)yeast phase melanin, establish their black element of training system, and study whether melanization influence the sensitivity of antifungal drugs,for the study of pathogenic mechanism PM to provide the theory basis.Method Two strains of PM (standard strain FRR and clinical isolate strain GXMU110608) were grown on a chemically defined liquid medium supplemented with/without1.0mM L-3,4-dihydroxyphenylalanine (L-DOPA) and on a brain heart infusion (BHI) agar supplemented with/without1.0mM L-DOPA,to train yeast cell,in order to observe the change of colonies, medium and ultrastructure.Then an antifungal drug susceptibility test in vitro had been conducted for the melanized and nonmelanized PM with the antifungal drugs like fluconazole (FCZ)、 Itraconazole (ICZ) and amphotericin B (AMB).Results (1) Two tested strains on chemically defined liquid medium shock train at37℃for15days, the color of the liquid medium with L-DOPA was dark brown or black, while the color of the liquid medium without L-DOPA was the basic coloration.(2) Two tested strains on BHI train at37℃for10days,the color of the colonies with L-DOPA deeper than the colonies without L-DOPA, and black pigment appear around the colonies.(3)Yeast cells grown with and without L-DOPA have no difference was observed in optical microscope.(4) Yeast cells grown with and without L-DOPA have no difference was observed in scanning electron micrographs.(5) Transmission electron micrographs of yeast cells grown with and without L-DOPA. The cell walls and cytoplasm of yeast grown with L-DOPA were coated with electrondense granules, diameter is about100nm. The microbodies of yeast grown with L-DOPA expanded significantly, electrondense granules in the microbodies and the core parts increased significantly,but no or few electrondense granules deposited in the cell walls and cytoplasm of yeast grown without L-DOPA,.(6)The MICs of the same drug AMB for the melanized and nonmelanized PM were not exactly the same,P<0.05.(7)No difference in the susceptibilities of melanized and nonmelanized PM to antifungal drugs FCZ and ICZ was observed using the MIC method,P>0.05.Conclusions (1) PM yeast produces a melanin-like pigment in the presence of L-DOPA,and secreted into the cells.(2)The microbody of yeast cells might be involved in the dopamine-melanin cell type in synthetic process, the melanin formation processing diameter is about100nm of the particle size distribution in the cell wall.(3)The increased synthesis of PM melanin may reduce the sensitivity of the PM to AMB in vitro.