Comparison and evaluation of enumeration methods for measurement of fungal spore emission

Estimation of fungal spore emission from various sources, which is a necessary input for the estimation of their effects on health and climate using mathematical models, relies on realistic quantification of fungal spores. Different quantification techniques have been used in various studies of fungal spore emission. For the purposes of model development, validation and application, the various methods must be correlated. In this study, we compare the commonly used methods - fluorescence microscopy, haemocytometer and fluorescence spectroscopy, in in relation to fungal spore emission estimation using Penicillium chrysogenum as a test fungal species. In addition, we also compare an offline and online technique - Biosampler® and Optical particle sizer (OPS) respectively. It was found that haemocytometer shows up to 50% higher average spore count than fluorescence microscopy in the range of 104–107 spores/ml. The effect of sampling volume, artifacts and image magnification on sample representativeness was also studied using fluorescence microscopy as the basis. Statistical analysis of these effects shows that at spore concentrations lower than 104/mL, the uncertainty is significant. The comparison between emission measurement using OPS and Biosampler/fluorescence microscopy techniques were reasonably similar. The quantitative comparison also provides a basis for other users to choose methods for their research objectives using appropriate quantitative correction and correlation factors.