Pigment activity investigation of Cryptococcus neoformans on red pitahaya (Hylocereus polyrhizus) agar

Abstract

Objective: Cryptococcus neoformans causes lifethreatening severe cryptococcosis in humans. These species are colonized in the nature and are spread from the environment to the host. Various media have been produced for the identification of C. neoformans. Yeast is easily identified due to the production of melanin in culture media containing pigment precursors. The red pitahaya (Hylocereus polyrhizus) which has just started to planted in our country has flavonoid pigments. In this study, it was aimed to evaluate the melanin pigment production of C. neoformans in the agar media prepared by newly defined from white and red pitahaya fruits. Methods: Molecularly confirmed thirteen environmental strains of C. neoformans were included in the study. In the study, in-house media were prepared from two different pitahaya [white pitahaya (Hylocereus undatus) agar (WPA) and red pitahaya) agar (RPA)] with mesocarp and endocarp parts of the fruits. Staib agar and potato dextrose agar media were used as positive and negative controls. Candida albicans has been used for nonpigmented yeasts. The strains were cultured in sterile 24-well polystyrene plates and pigment production was measured by Fiji/ImajeJ (GPLv3, NIH, USA) during one week. Results: It was observed that brown pigmented colonies, which can be easily separated from the nonpigmented C. albicans yeast colonies, were formed in the grown on KPA medium. Colony pigment formed in KPA medium was less than those formed on Staib agar. C. albicans colonies were larger on Staib agar, while C. neoformans formed more mucoid colonies on RPA. It was observed that the colony pigment formed in the RPA medium was less than the other in the cultivations on Staib agar and RPA medium. While RPA pigments are higher than WPA’s, the yeasts’ melanin production in Staib agar have higher data (p<0.05). No pigment production has been observed in PDA. Conclusion: Although the pigment production on RPA is less than on Staib agar medium, RPA can be used to demonstrate pigment production of C. neoformans. Descriptive media should be prepared with easily accessible inexpensive environmental resources containing phenolic chemicals for the research of pigment production of C. neoformans. © (2023), (Refik Saydam National Public Health Agency (RSNPHA)). All Rights Reserved.