職醫與工衛所CHEN, CHIH-CHIEHCHIH-CHIEHCHEN2008-10-132018-06-292008-10-132018-06-291998http://ntur.lib.ntu.edu.tw//handle/246246/83495The prevalence of bioaerosol particles has gained significant attention in the past decades and is considered to be a potential health hazard for people in a variety of environments, To identify and quantify airborne microorganisms, the bioaerosols are collected directly on semisolid culture media, or trapped from air into liquid substrates, followed by culturing, counting, and identification of the resulting colony forming units, Studies on error due to overcrowding of the colonies have concluded that the bias did not become significant until about 300 colonies/plate were present, but no study has taken the non-homogeneity of colony size into account, In the present study, a Cartesian coordinate system was used to simulate the surface area of standard 100 mm diameter colony culture plates and the colonies growing on them, A resolution of 1000 x 1000 was found to be accurate enough to represent the actual size of the colony, The capacity of distinguishing overlapping colonies (defined as resolution index) the covering fraction, the colony surface density, and the colony size distribution were among the primary parameters investigated in this study. The counting efficiency was found to consistently decrease with increasing surface density and decreasing resolution index, The recommended upper Limit of colony counts on each plate depended not only on the number concentration but also the size distribution of the colonies. To have a minimum counting efficiency of 95%, the colony densities should not exceed 1290, 200 and 71 colonies/plate, for colony sizes of 2, 5 and 8 mm, respectively. This was based on the assumption that the colony size was uniform and resolution index was 0.8. As the geometric standard deviation (GSD) kept increasing, the Larger GSDs resulted in higher covering fraction, and thus, lower counting efficiency. This phenomenon was independent of resolution index. (C) 1998 British Occupational Hygiene Society. Published by Elsevier Science Ltd.en-USAIRBORNEjournal article