Sampling of biological particles

Abstract

Sampling strategy, sampling and analysis of different biological particles, mainly fungal spores and bacteria, are reviewed. The sampling is strongly dependent on the environment, time of year and activity at the workplace. The choice of suitable sampling equipment depends on the levels of airborne micro-organisms. For sampling in non-industrial indoor environments (<10⁶ micro-organisms m^–3), slit samplers, cascade impactors and multistage impingers can be used. At high concentrations of airborne micro-organisms (>10⁶ micro-organisms m^–3), other types of methods must be used because the slit samplers and cascade impactors, such as Andersen samplers, are often overloaded. Sampling using polycarbonate filters is one method that can be used. Other useful methods are, for example, multistage liquid impingers or an Aerojet General Glass Cyclone. Analysis of the filter by cultivation gives lower values than microscopy. Direct analysis of the filter by scanning electron microscopy results in values that are 2–3 times higher than those obtained by analysis using Acridine Orange staining and epifluorescence microscopy. Suspension of biological particles in liquid before microscopic analysis results in the observation of more single spores, which suggests that large spore aggregates break down during suspension.