Evaluation of different culture media supporting the growth and melanin production in Cryptococcus

Background and objectives Melanin, as a virulence factor, plays an important role in protecting Cryptococcus against the host immune response. The demonstration of a melanin-producing colony in vitro helps in proper identification of this fungus. This study aimed to assess 3 locally available natural seeds in designing a culture medium for supporting growth of Cryptococcus and melanin production. Methods Cryptococcus neoformans previously identified and stocked were tested on flaxseed, black til, and Garden cress containing culture medium separately, where Niger seed agar served as positive control. Melanin production was visually measured using direct observation and also using Whatman No.1 filter paper. The quantitative measurement was done by using spectrophotometric analysis after 48 h of incubation at 37℃. Results All three seed-based culture media developed for Cryptococcus supported its growth, and melanin production was significantly more in colonies grown on garden cress agar than on black til and flaxseed agar. Difference between garden cress medium and Niger seed medium was not significant (P=0.818). Interpretation and conclusions Garden cress seed agar was found to be suitable for supporting melanin production in Cryptococcus neoformans. Further use of these seeds in preparation of readymade dehydrated medium can also be elucidated.