Study of the effects of vacuuming on the concentration of dust mite antigen and endotoxin

Dust mite antigens are major sources of allergens in house dust and together with endotoxin, a proinflammatory component of gram negative bacteria also found in house dust, are important causes of tissue injury involved in the pathogenesis and severity of allergic diseases, eg, asthma.

To determine the effectiveness of vacuuming in reducing the quantity of dust mite antigens, Dermatophagoides pteronyssinus (Der p and Der p2) and endotoxin using a quantitative ELISA assay and to correlate results with those obtained using a qualitative rapid dipstick method for Der p2.

Four specimens of house dust were collected using a Kirby Model G5 vacuum cleaner with a Micron Magic Filtration system from an approximately 54" x 18" standardized area of rug from each of 20 homes at 4 time intervals over a 6-week period, ie, a baseline specimen #1 at 0 week; specimen #2 at 1 week; specimen #3 at 5 weeks (1 month after specimen #2); specimen #4 at 6 weeks (1 week after specimen #3). Three intervals were compared, ie, period 1-2 (1 week), period 2-3 (1 month), and period 3 to 4 (1 week). The concentrations of Der p1 and Der p2 were determined in dust samples using a standard ELISA assay and the concentration of endotoxin was detected using a limulus amebocyte lysate assay. Concentrations of Der p2, determined by the standard ELISA assay, were compared to those in the same samples determined by a rapid dipstick method.

A wide range of values for total weight of unprocessed dust (0.3 to 59 g, X = 8.7) and finely sieved dust (0.1 to 19 g, X = 3) from all specimens were found. In finely sieved dust specimens the mean concentrations of Der p1, Der p2 and endotoxin were 775, 1310, and 3836 ng/g of dust, respectively. Following weekly vacuuming there was an increase in concentration of Der p1, Der p2, and endotoxin in 20%, 35%, and 63% of the houses, respectively, compared to in monthly vacuuming in which increases were seen in 65%, 50%, and 63% of the houses, respectively. In contrast, there was a decrease in concentration of Der p1, Der p2 and endotoxin with weekly vacuuming in 43%, 60%, and 37% of the houses respectively versus in monthly vacuuming in 15%, 35%, and 37% of the houses respectively. A correlation coefficient of 0.7 was found for the concentration of Der p2 in 37/40 samples tested detected using the ELISA method compared with rapid dipstick assay.

The results of this study support the effectiveness of vacuuming on the reduction of dust mite antigens (Der p1 and Der p2) ie, Der p2 > Der p1. This reduction was more pronounced with weekly compared with monthly vacuuming. No reduction in the concentration of endotoxin was found. A good correlation was found between results obtained by ELISA and rapid dipstick assay for Der p2.