Microflora and acarofauna of bed dust from homes in Upper Silesia, Poland

Pyroglyphid mites are considered a major cause of house dust allergy. The occurrence and possible pathogenic role of other biologic components of house dust, in particular bacteria, has received less attention.

The aim of this study was to examine bacteria present in the samples of house dust from beds, in comparison to fungi and mites recovery.

Samples of bed dust were collected from 40 homes in Upper Silesia (Poland). Of these, 19 came from the homes of people with asthma caused by house dust and 21 from the homes of people without allergy. The concentrations of bacteria, fungi, mites, and endotoxin and species composition of microflora and acarofauna were determined.

The overall mean concentrations of mesophilic bacteria, thermophilic bacteria and fungi, including yeasts, were, respectively, 1.6 x 10(6), 1.7 x 10(3), and 1.6 x 10(4) CFU/g. Samples contained an average of 8.4 mites/g and the ten samples assayed for bacterial endotoxin averaged 80.4 ng/mg. A total of 55 species of bacteria, 40 of fungi and 13 of mites were found. Gram-positive cocci (mostly Staphylococcus spp.) were the predominant mesophilic bacteria, followed by corynebacteria and Bacillus spp. Thermophilic bacteria were represented only by actinomycetes, with Thermoactinomyces vulgaris predominant. The most numerous fungi were Penicillium spp. and Aspergillus spp. followed by yeasts. The most abundant mites were Dermatophagoides spp. which formed > 85% of the total count. There were no significant differences between the homes of allergic and nonallergic people in the concentrations of total bacteria, fungi, and mites. Bacillus, Aspergillus and total filamentous fungi (molds), but not yeasts, were significantly more numerous in the homes of people with asthma caused by house dust.

The results suggest that some species of bacteria and filamentous fungi should be considered potential causes of house dust allergy.