Long-term sampling of airborne bacteria and fungi into a non-evaporating liquid

Conventional sampling of bioaerosols into liquid impingers can only be perf ormed with water or another low-viscosity liquid as the collection medium. Since these liquids evaporate quickly, sampling is generally limited to sho rt-time periods of 15-30 min. In this study, our recently developed "BioSam pler", has been used with a non-evaporating, higher viscosity liquid that d oes not kill nor grow microorganisms, and thus has been used to sample airb orne bacteria and fungi for several hours. In side-by-side comparisons with the conventional AGI-30 impinger, sampling indoor air environments over sh ort-time periods, the BioSampler yielded equivalent or higher culturable co unts for bacteria and fungi than the AGI-30 when both samplers were operate d for 30 min with 20 ml of phosphate buffer as the collection medium. The b io-efficiency of the AGI-30 decreased rapidly with sampling time until the liquid had evaporated after about 1 1/2 h. When the BioSampler was operated for 4 h with non-evaporating heavy white mineral oil, the collection effic iency decreased only moderately due to minimal reaerosolization of collecte d particles and gentle collection of the viable microorganisms. Samples obt ained through long-term sampling with the BioSampler may detect culturable bacteria and fungi at lower ambient concentration levels than is possible t hrough conventional liquid impingement sampling over short-time periods. (C ) 1999 Elsevier Science Ltd. All rights reserved.