Identification of Penicillium marneffei in Children and Antifungal Susceptibility of Yeast form of Penicillium marneffei

Objective To identify the Penicillium marneffei(PM) pathogen isolated from the children and determine the antifungal susceptibilities of the yeast form of Penicillium marneffei by E-test method and guide to select suitable antifungal agents for clinic treatment.Methods The blood or bone marrow samples were examined directly and incubated at 25℃ and 37℃,respectively for culturing the fungal pathogens.The growth and colonial morphology of PM was inspected and the characteristics of PM smear were observed under microscope.According to the E-test method NCCLS M27-p document,the MICs of yeast form of the 6 Penicillium marneffei to the 5 antifungel agents(itraconazole,ketoconazole,5-fluorocytosine,fluconazole,amphotericin B) were determined.Results PM is a thermally dimorphic Penicillium.Under 25℃ it is mycelial form.Under 37℃ it is yeast form.The two forms have its typical colonial morphological characteristics.The spore is round or ellipsoidal or sausage-like.And the size is about 2～8 μm.In the Wright's staining,cell wall of PM is violet,distinct and continuous.There are transparent transverses septums in sausage-like spore.The MIC ranges of itraconazole,ketoconazole,5-fluorocytosine,fluconazole,amphotericin B on yeast form were determined as 0.002～0.016 μg/mL,0.012～0.125 μg/mL,0.032～0.380 μg/mL,1.500～6.000 μg/mL and 0.047～2.000 μg/mL,respectively.There were 1 stain resistant to ketoconazole and 5-fluorocytosine and 2 stains resistant to amphotericin B.Conclusion PM's typical colonial morphology and fungal spore in bone marrow and peripheral blood are important features for identification.The pathogen is more susceptibile to itraconazole than to the other 4 antifungal agents.