ObjectiveTo understand the identification and in vitro antifungal susceptibility of Penicillium marneffei(PM) in yeast phase, and guide clinic antifungal application. MethodsStrains isolated from blood and bone marrow of 23 patients infected with PM in a hospital between 2009 and 2016 were collected, colony morphology of PM in yeast phase was observed, susceptibility to itraconazole, voriconazole, amphotericin B, and fluconazole were detected with Etest method.ResultsColony morphology of PM were as follows: direct microscopic examination of Wright’s staining of tissue specimens found visible oval or round spore with apparent septum, and mainly located in macrophage; Gram staining of blood culture specimens found that strains were with bulbous and slightly curved ends, occasionally branched and with septum. PM was dimorphic fungi, presented mycelium at 28°C, produced red pigment and diffused into medium; PM presented yeast form at 35°C, there were typical colony morphology. Minimum inhibitory concentrations (MICs) of itraconazole, voriconazole, amphotericin B, and fluconazole to PM in yeast phase were 0.002-0.016, 0.012-0.125, 0.002-0.500, and 0.500-16.000 μg/mL respectively.ConclusionTypical colony morphology and fungal spore of PM in bone marrow and peripheral blood are important features for identification. PM is most susceptible to itraconazole, followed by voriconazole and amphotericin B, while fluconazole is less susceptible.