Mould-devouring mites differ in guanine excretion from dust-eating acari, a possible error source in mite allergen exposure studies

Background and Objective: Measurement of guanine in dust proved a good assessment of mite allergen exposure. Methods: Exposure to mite allergens may lead to atopic inflictions. In a semi-natural test system the development of Dermatophagoides pteronyssinus (Trouessart) and Glycyphagus domesticus (De Geer), and the presence of their guanine excretion, was examined in a dustsoiled and mouldy environment. Mites were counted after heat-escape, and guanine was detected by means of capillary zone electrophoresis. For each species, 50 mites randomly taken, were inoculated on soiled test-surfaces of 10 × 10 cm. Rough wooden board, gypsum board, tufted carpet, and a self-made mattress representing wall surfaces and home-textiles, respectively, were used. Eight weeks after inoculation with mites only, the surfaces were all mould ridden, and mite and guanine measurements were taken. The Spearman rank correlation test and the Mann-Whitney U-test were used in statistical analysis. The confidence limit was set at 1%. Results: Among the various test-surfaces, no differences were found regarding total mite numbers and amount of guanine present (P > 0.0l). For the dust-eating mite D. pteronyssinus, total mite numbers correlated with the amount of guanine present (P= 0.002) on all inoculated surfaces, indicating feeding on the protein-rich dust. For the mould devouring mite G. domesticus, however, no such correlation was found (P= 0.72). Apparently, they mainly consumed fungal carbohydrates during this experiment. Conclusion: The allergological relevance of storage mites has been under discussion for the last 25 years. In humid homes, these mites will feed almost exclusively on fungi and may produce allergenic or irritating substances different from those arising on protein-rich laboratory media used in allergen extract production or present in carpets, bedding and furniture.