A comparison of sampling media for environmental viable fungi collected ina hospital environment

Quantitative evaluation of fungal exposure is often conducted by analysis o f the composition of microbes in air samples and calculation of the concent rations afterward. The collecting medium that favors the growth for most sa prophytic fungi is considered to be the ideal choice in most circumstances. Currently, the culture medium most frequently adopted in environmental sam pling for airborne fungi is MEA (malt extract agar) recommended by the ACGI H for its suitability for most fungal growth. DG18 (dichloran glycerol-18), developed in 1980, is suggested for growth at lower water activity (a(w) = 0.95) specifically and is not as commonly used in general studies. This in vestigation collected airborne viable fungi using a single stage/N6 Anderse n impactor with MEA and DG18 agar plates attached simultaneously to the sam e set of samplers. The sampling locations were at 17 sites within a central air-conditioned hospital. After incubation and morphological identificatio n, concentrations of airborne fungi and bacteria were expressed as CFU/m(3) (colony forming units/m(3)). There are 405 DG18 plates and 378 plates avai lable for statistical analysis. Results show that the airborne fungal conce ntrations, shown by geometric mean (GM), are higher from the DG18 plates th an from the MEA plates. The total fungal concentrations is 68.6 vs 12.94 CF U/m(3), and for Aspergillus spp., the concentration is 1.58 vs 0.72 CFU/m(3 ); for Penicillium spp., 3.37 vs 0.71; and for yeast, 5.09 vs 0.49 CFU/m(3) . In addition, the number of different genera present is greater on the DG1 8 plates than on the MEA plates, on average, 2.85 types vs 1.72. This study suggests that in a hospital environment with 24-h, central air conditionin g, DG18 plates appear to be more effective in collecting more fungal coloni es in terms of both quantity and types of genera. Such a finding is presume d to be attributed to the characteristic of DG18 in slowing colony growth s o that the dominating genus will not over occupy the culture plate surface before the less competitive genus can fully develop. Future studies on rela ted biological mechanisms are essential to conclude whether the above resul ts sustain when sampling is conducted in other environments. (C) 2000 Acade mic Press.