Quantitative PCR analysis of fungal DNA in Swedish day care centers and comparison with building characteristics and allergen levels.

ABSTRACT

Abstract Sweden has had allergen-avoidance day care centers (AADCs) since 1979. The aim of this study was to measure fungal DNA by quantitative polymerase chain reaction (qPCR), a new method, in AADCs and ordinary day care centers (ODCs) and examine associations between allergen levels and building characteristics. Dust samples were collected by swabbing doorframes, vacuum-cleaning, and using Petri dishes. In total, 11 AADCs and 11 ODCs were studied (70 rooms). Total fungal DNA, measured by qPCR in the swab dust, was detected in 89%, Aspergillus or Penicillium (Asp/Pen) DNA in 34%, and Stachybotrys chartarum DNA in 6% of the rooms. Total fungal DNA was significantly higher in rooms with linoleum floor (P = 0.02), textile carpets (P = 0.03), reported dampness/molds (P = 0.02) and reported odor (P < 0.001) in the buildings, and significantly lower in wooden facade buildings (P = 0.003). Reported odor was related to the amount of sieved fine dust, reported dampness/molds and type of building construction. Total fungal DNA was related to cat, dog, horse and total allergen levels (P = 0.003) in the day care centers. In conclusion, total fungal DNA is related to reported dampness/molds, reported odor, and type of wall construction. The association between fungal and allergen contamination indicated a general 'hygiene factor' related to biological contaminants. Practical Implications The associations between fungal DNA, reported dampness/molds, and odor support the view that buildings with odor problems should be investigated for possible hidden fungal growth. There is a need to measure fungal biomass in different types of building constructions by monitoring fungal DNA. Analysis of fungal DNA with quantitative PCR can be a fast and practical way to study indoor fungal contamination. Swabbing dust from the doorframe of the main entrance to the room can be a convenient method of sampling dust for fungal DNA analysis. The high prevalence of reported dampness/molds and the common occurrence of fungal DNA indicate the need to improve the indoor environment of Swedish day care centers.