title: Diagnostic medium containing inositol, urea, and caffeic acid for selective growth of Cryptococcus neoformans.
abstract: An agar medium containing inositol and urea as sole carbon and nitrogen sources, caffeic acid and ferric citrate as agents for the selective pigmentation of Cryptococcus neoformans, gentamicin as a broad-spectrum bacterial antibiotic, and yeast nitrogen base without amino acids and ammonium sulfate (Difco) was tested against 137 clinical isolates, 4 survey specimens, and 11 ATCC yeast and yeast-like strains. All 28 strains of C. neoformans showed heavy growth and dark brown pigmentation after 36 h. All other tested species of Cryptococcus showed heavy growth after 36 h but only light brown pigmentation after 48 h. No growth was observed in any tested strains of Geotrichum, Pityrosporum, Rhodotorula, Saccharomyces, and Torulopsis. Only the Cryptococcus-like Candida humicola grew of the 8 species and 62 strains of Candida tested. Six of 15 strains of Trichosporon cutaneum and 1 of 2 strains of Trichosporon pullulans showed moderate growth after 48 h. Very different colonial and microscopic morphology and/or the absence of brown pigmentation easily differentiated these strains of T. cutaneum, T. pullulans, and C. humicola from C. neoformans. The growth- and pigmentation-providing characteristics of the medium were unaffected by 2 h of exposure to 254 nm of ultraviolet light.
mesh_terms: D000362:Agar; D002109:Caffeic Acids / Q000378:metabolism; D002951:Citrates; D003453:Cryptococcosis / Q000175:diagnosis; D003454:Cryptococcus / Q000254:growth & development*; D003455:Cryptococcus neoformans / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D003937:Diagnosis, Differential; D005290:Ferric Compounds / Q000378:metabolism; D006801:Humans; D007294:Inositol / Q000378:metabolism; D010860:Pigments, Biological / Q000096:biosynthesis; D013045:Species Specificity; D014466:Ultraviolet Rays; D014508:Urea / Q000378:metabolism
chemical_list: D002109:Caffeic Acids; D002951:Citrates; D005290:Ferric Compounds; D010860:Pigments, Biological; D007294:Inositol; D014508:Urea; D000362:Agar