Evaluation of Air Samplers for Recovery of Artificially Generated Aerosols of Pure Cultures in a Controlled Environment

Abstract

All Glass Impinger-30 (AGI-30), Andersen 6-stage Sieve Air Sampler (Andersen impactor), Reuter centrifugal air sampler (RCS sampler), and Millipore open type membrane filter sampler (Filter sampler) were evaluated for recovery of artificially-generated aerosols of pure cultures of Pseudomonas fluorescens, Escherichia coli, Streptococcus faecalis, and endospores of Bacillus subtilis. Size distribution of the aerosol was analyzed to determine its relationship to air sampler efficiency. Five min after the spray, 71 to 85% of particles were between 1.1–3.3μm in size and 3.5 to 10.4% were smaller than 1.1μm in size. The Andersen impactor recovered significantly greater numbers of nonsporeforming bacteria, with least variability of recovery and the RCS sampler recovered significantly smaller numbers and exhibited greatest variability of the four samplers tested. AGI-30 and Filter sampler performance varied depending on the species tested. For recovery of bacterial endospore, the Filter and Andersen samplers both recovered greater numbers than the AGI-30 and RCS sampler. The RCS sampler recovered a significantly lower number of spores with the most variable results of the four samplers. Our data indicate that the Andersen impactor is the sampler of choice for recovering microbial aerosols of interest to the food processing industry.