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QUANTITATIVE PCR ANALYSIS OF HOUSE DUST CAN REVEAL ABNORMAL MOLD CONDITIONS
Citation:
Meklin, T, R A. Haugland, T. Reponen, M Varma, Z. Lummus, D. Bernstein, L J. Wymer, D. Dearborn, AND S J. Vesper. QUANTITATIVE PCR ANALYSIS OF HOUSE DUST CAN REVEAL ABNORMAL MOLD CONDITIONS. JOURNAL OF ENVIRONMENTAL MONITORING. Royal Society of Chemistry, London, Uk, 6(7):615-620, (2004).
Impact/Purpose:
To understand children's risks from exposure to molds in their environment and to explore risk management options for mitigating those risks.
Description:
Indoor mold populations were measured in the dust of homes in Cleveland and Cincinnati, OH, by quantitative PCR (QPCR) and, in Cincinnati, also by culturing. QPCR assays for 82 species (or groups of species) were used to identify and quantify indoor mold populations in moldy homes (MH) and reference homes (RH). About 65% of the species were never or only rarely detected. The ratios (MH geometric mean/ RH geometric mean) for 11 species (Aspergillus fumigatus, A. ochraceus, A. penicilliodes, A. restrictus, A. sclerotiorum, A. unguis, A. versicolor, Eurotium group, Penicillium purpurogenum, Cladosporium sphaerospermum and Stachybotrys chartarum) were >1 in both cities. However, the same ratios for 10 species (Aspergillus ustus, Penicillium chrysogenum type 2, Acremonium strictum, Alternaria alternata, Cladosporium cladosporiodes types 1 and 2, C. herbarum, Epicoccum nigrum, Mucor and Rhizopus group, and Rhizopus stolonifer were consistently <1. SAS Proc_Probit analysis of the sum of the logs of the populations of these two groups resulted in a 95% probability range for separating MH from RH. These results suggest that it may be possible to evaluate whether a home has an abnormal mold condition by quantifying a limited set of mold species in a dust sample.
Mold growth in homes, schools and buildings has become a controversial health issue with some studies suggesting negative health effects (1, 3, 6, 20, 25, 28, 29). Some of the reasons for the controversy may include the large number of molds that occur indoors and the difficulties involved with measuring their populations.
Traditionally indoor mold populations have been measured with culturing methods that are based on colony counting and microscopic identification (16, 18, 19, 21, 22, 27). However, culture methods are time consuming and normally only limited information on fungal species is obtained. In addition, viable microbes represent only a small fraction of the total molds present (26). More accurate, specific and faster methods are needed to analyze environmental samples for molds.
A DNA-based method for quantitative measurement of different species of indoor molds has been developed at the United States Environmental Protection Agency (11). The system is based on real time monitoring of the polymerase chain reaction (PCR) using fluorigenic 5' exonuclease chemistry (TaqManTM) (14) that allows for highly quantitative results (10, 12, 13, 23). This technology, called quantitative PCR (QPCR) is now being applied to environmental analysis of samples, including dust.
House dust samples may better represent cumulative exposures to molds compared to short air samples (5, 7). Findings showing the gradual increase of mold concentration in floor dust, despite of regular vacuuming (4), strengthen the idea of house dust samples as reservoir of fungal contamination. In this study, QPCR technology was used to quantify 82 mold species in dust samples in MH and RH in Cleveland and Cincinnati, OH.
