Production of the mycelial phase of Malassezia in vitro.

To study the pathogenicity of Malassezia, the agent of pityriasis versicolor, it is necessary to obtain the mycelial form in vitro. A range of different components and conditions were tested to induce yeast cells of the organism to produce mycelia in vitro using different culture media. A mycelial culture medium was developed that consisted of bacteriological peptone, glucose, yeast extract, ox bile, glycerol, glycerol monostearate, Tween 80, squalene, glycine, potassium nitrate, sodium chloride, ferrous sulphate and magnesium sulphate with or without agar. The liquid and solid medium had a pH of 5.6 and the temperature of incubation was 30 degrees C. Cultures were incubated in air. This medium was able to induce some strains of Malassezia to produce up to 40% mycelium in vitro. In total, 33 different strains of Malassezia obtained from the skin of the healthy individuals and patients with pityriasis versicolor were tested for mycelium production. The strains of Malassezia capable of producing mycelium in vitro all possessed the serovar A antigen.