A modified method for testing inositol assimilation by Cryptococcus species.

The proposed method for rapid testing of inositol assimilation incorporates shake cultures in an indicator-based broth containing inositol (1%), yeast nitrogen base (0.067%), bromocresol purple, and a heavy inoculum. Of 153 yeast isolates investigated, inositol assimilation was shown with the modified method, as also by the Adams-Cooper procedure, in all the 123 isolates, representing 11 species of Cryptococcus. The results were negative by both the methods in the remaining 30 isolates belonging to Candida, Rhodotorula, Torulopsis, Pichia, Saccharomyces, and Sporobolomyces. The modified method was found to be significantly more effective than the Adams-Cooper procedure; the results could be read within 36 h by the former as against 336 h by the latter method. The superiority of the modified method to the Adams-Cooper procedure is attributed to increased aeration in shake cultures, a heavier inoculum, and reduced concentration of yeast nitrogen base.