Use of an Andersen Bioaerosol Sampler to Simultaneously Provide Culturable Particle and Culturable Organism Size Distributions

摘要

A method is provided for estimating size distributions in terms of both culturable particles (CP) and culturable organisms (CO) from a single sample collected with an Andersen bioaerosol impactor. Half of the agar surface of each Petri dish is covered with a polycarbonate filter substrate through which liquid from the agar can wick and thereby form a flat wetted collection surface, and the other half of the agar surface is uncovered. Quantification of CO distribution results involves washing the collected particles from the filter surfaces and plating suitable dilutions of de-agglomerated particles, followed by incubating the organisms, and counting the resulting colonies; whereas, quantification of CP results is based on direct culturing of the agar media. Experiments were conducted with near-monodisperse clusters of Bacillus atrophaeus (aka BG) aerosols covering APS-determined geometric number mean sizes from 1.83 to 8.7 μm aerodynamic diameter (AD). There is little difference between the Andersen-determined median sizes of the CO and CP distributions of the near-monodisperse clusters, which supports the utility of the CO method. The method was applied to sampling bioaerosol in a previously occupied classroom and the results showed median sizes of 1.7 and 3.1 μm AD for the CP and CO distributions, respectively. Total bioaerosol concentrations were 0.53 and 3.4 CO/L, respectively, so the average CP contained 6.4 CO.