Cottonseed extract versus pharmamedia for the in vitro mould-yeast conversion of Blastomyces dermatitidis.

A cottonseed medium, based on a 1% aqueous extract of seeds of any of the eight indigenously available varieties of cotton belonging to Gossypium hirsutum or Gossypium arboreum, was evaluated for the mould-yeast conversion of Blastomyces dermatitidis in vitro, and compared with pharmamedia agar as a control. The cottonseed agar was found to be as efficient as pharmamedia agar for the mould-yeast conversion of the 19 B. dermatitidis strains tested. Therefore, cottonseeds provide an adequate and inexpensive substitute for pharmamedia for the mould-yeast conversion of B. dermatitidis. It should be noted that the term 'cottonseed' medium has been used rather loosely in the literature and that this medium is based on pharmamedia and not on a cottonseed extract. The authors suggest that media based on pharmamedia should be referred to as pharmamedia agar and the use of the term 'cottonseed' should be restricted to media containing cottonseed extract.