The effect of freezing and the influence of isolation medium on the recovery of pathogenic fungi from sputum

Abstract

The primary objective of this study was to determine whether freezing sputa in dry ice had any effect on the recovery of pathogenic fungi. Sputa seeded with each of five fungi (Histoplasma capsulatum, Blastomyces dermatitidis, Cryptococus neoformans, Coccidioides immitis, and Aspergillus fumigatus) were frozen and stored for 24, 48, and 72 hours on dry ice. H. capsulatum was killed, and only a few colonies of B. dermatitidis and C. neoformans were isolated from these sputa. However, A. fumigatus and C. immitis withstood the effects of freezing. A second objective was to compare the recovery of all five fungi from seeded sputa stored at room temperature for 24, 48, and 72 hours, on yeast extract-phosphate agar with NH4OH and on Sabhi agar. The yeast extract-phosphate agar with NH4OH was superior to Sabhi agar, for the isolation of all fungi studied, except A. fumigatus.