Influence of storage on the fungal concentration determination of impinger and filter samples.

The effects of storage on concentrations of airborne fungal samples were evaluated in a laboratory test chamber. Spores of Penicillium citrinum and cells of Candida famata var. flareri were aerosolized by a Pitt-3 generator and a Collison nebulizer, respectively. The evaluated sampling methods were AGI-30 impingers, Nuclepore filters, and gelatin filters. The effect of storage time was determined as the ratio, C(t)/C(0), where C(t) and C(0) were the total counts or colony concentrations of the simultaneously collected samples stored for t and 0 hr, respectively. In addition, the effect of storage temperature was investigated by storing AGI-30 and filter samples at 25 and 4 degrees C. The results demonstrated that the culturability of Penicillium spores in the impinger samples decreased as storage time increased. In contrast, the Candida yeast cells could survive and reproduce more cells in the impinger fluid. Moreover, it was observed that refrigeration of the impinger samples could inhibit the growth rate of collected cells. Therefore, it was suggested that the impinger samples should be refrigerated and processed as soon as possible to avoid the loss of spore culturability or the increase of yeast cells. Regarding the filtration methods, the effect of storage time and temperature for Penicillium spores was demonstrated to be insignificant. However, Candida yeast recovery from filters was found to decrease as storage time increased.