Phagocytosis and Killing of Human Pathogenic, Penicillium marneffei and Non-pathogenic, Penicillium citrinum by Mouse Macrophage J774.1 Cells

Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand. Received for publication: February 14, 2008. Reprint request: Prof. Dr. Nongnuch Vanittanakom, Department of Microbiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand. Email: [email protected] Keyword: Penicillium marneffei, Penicillium citrinum, phagocytosis, killing, J774.1 ABSTRACT In this study, we examined in vitro phagocytosis and killing activity of mouse macrophage cells against conidia of pathogenic Penicillium marneffei, and compared this with non-pathogenic Penicillium citrinum. Phagocytosis and killing assays were determined using microscopy and viable colony plate counts. The results indicated a highly efficient phagocytosis effect of J774.1 cells against both species of Penicillium. There was no difference between the percentages of cells phagocytosed in both species. The phagocytic indices of P. marneffei at 60, 120, and 240 minutes of infection were significantly higher than those of P. citrinum. However, in the early stages of phagocytosis, the percentage killing of P. marneffei was significantly lower than that observed in P. citrinum. Conidia of P. marneffei were more susceptible to being phagocytosed but also more resistant to killing by macrophages than those of non-pathogenic Penicillium. The mechanism of intracellular survival or resistance to killing by macrophages needs further investigation. (J Infect Dis Antimicrob Agents 2008;25:81-9.)