Microscopic morphologies of different switched-phenotypes in Candida dubliniensis

Background and Objective: Candida dubliniensis is an opportunistic pathogen originally isolated from AIDS patients and has ability to invade and cause systemic disease in immunocompromised patients as Candida albicans does. Phenotypic switching phenomenon, one of the essential virulence factor, has been firstly found in Candida albicans . It seems to play a role in the switching of Candida from normal flora to pathogenic form. This study has focused on morphologies of different phenotypes during phenotypic switching in Candida dubliniensis . Method: Total 36 isolates of Candida dubliniensis were tested on an indicator medium containing 1 mM CuSO 4 . Cellular morphologies of variant switched-phenotypes were observed under the microscope (400X) by lactophenol cotton blue staining. Result : It was found that the phenotypic switching system in Candida dubliniensis included white (Wh), light brown (LB), dark brown (DB), wrinkle (Wr), fuzzy light brown (Fz) and brain-like appearance (Br) phenotypes. When cell morphologies in each switched phenotypes were observed under the microscope, it was found that white phenotype showed much hyphae production, while other types showed budding yeast form. Conclusion : This study has suggested that filamentous form is more penetrating capable than budding yeast form, thus white phenotype is possible to be a pathogenic form of Candida dubliniensis . However, for more understanding of the pathogenesis, the virulence in each phenotype other than morphogenesis have been further studied. Key words: Candida dubliniensis , phenotypic switching, morphology