Preliminary study on the concentration and species composition of bacteria, fungi and mites in samples of house dust from Silesia (Poland).

Twenty-one samples of house dust collected from dwellings situated in Upper Silesia (Poland) were subjected to bacteriological, mycological and acarological examination. Moreover, in two samples the concentration of bacterial endotoxin was estimated by the use of Limulus test. The mean concentration of bacteria in the examined samples was 2831.9 thousands cfu (colony forming units) per gram, that of fungi - 28.4 thousands cfu per gram, and that of mites - 51.5 specimens per gram. No significant correlation could be found between the numbers of these three components of house dust. Two examined samples of house dust contained high amounts of bacterial endotoxin which are comparable to the concentration of endotoxin in agricultural dusts, and could be of immunopathogenic significance. In the bacterial flora of the examined house dust samples, staphylococci prevailed in 45.9% of all isolates, streptococci (23.2%), corynebacteria (13.9%) and spore-forming bacilli (12.2%). Among fungi, the most numerous were strains of the genus Penicillium (39.4%), yeasts (29.5%) and strains of the genus Aspergillus (8.4%). Both bacteria and fungi comprise species that are known for their allergenic properties. The mite fauna of the examined samples was dominated by Dermatophagoides farinae (62.7% of all specimens) and Dermatophagoides pteronyssinus (30.4%); both species are known as important allergens of house dust. The results hitherto obtained indicate the potential significance of all the investigated components (bacteria, fungi and mites) in causing allergy to house dust.