Comparative Mold and Yeast Recovery Analysis (The Effect of Differing Incubation Temperature Ranges and Growth Media)

Abstract

Environmental monitoring methodology for recovering fungal organisms often dictates the use of a selective medium incubated at ambient temperatures (20–25°C) for as many as seven days incubation to ensure reliable recovery. However, these methods (which must remain standardized for identification purposes) are not the only avenue environmental monitoring programs may follow. This study comparatively analyzed recovery rates of fungal organisms cultured on both a general purpose bacteriological nutrient medium (Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80), and on a medium selective for the growth of yeasts and molds (Sabouraud Dextrose Agar). The bacteriologic medium was incubated at elevated temperatures (30–35°C) for 70–72 hours then transferred to ambient temperatures for another 70–72 hours incubation. The control case selective medium was incubated solely at 20–25°C for 110–130 hours. Additionally, in a separate test the selective medium was incubated at the same temperature and time specifications as the bacteriologic medium to analyze recovery capabilities. Equivalent or better recovery was obtained for all test panel organisms of yeasts and molds using Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80 incubated at 30–35°C. Equivalent or better recovery was obtained for eight of the nine test panel organisms of yeasts and molds incubated at elevated temperatures on Sabouraud Dextrose Agar versus recovery on Agar versus recovery on Sabouraud Dextrose Agar incubated solely at 20–25°C. No inhibition of growth was observed at the elevated temperature range of 30–35°C. Three days incubation at elevated temperatures was a sufficient incubation period to detect the test organisms cultured on Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80.