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QUANTITATIVE PCR OF SELECTED ASPERGILLUS, PENICILLIUM AND PAECILOMYCES SPECIES
Citation:
Haugland, R A., M Varma, L J. Wymer, AND S J. Vesper. QUANTITATIVE PCR OF SELECTED ASPERGILLUS, PENICILLIUM AND PAECILOMYCES SPECIES. SYSTEMATIC AND APPLIED MICROBIOLOGY 27(2):198-210, (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:
A total of 65 quantitative PCR (QPCR) assays, incorporating fluorigenic 5' nuclease (TaqMan®) chemistry and directed at the nuclear ribosomal RNA operon, internal transcribed spacer regions (ITS1 or ITS2) was developed and tested for the detection of Aspergillus, Penicillium and Paecilomyces species that have been reported in indoor environments. The assays varied in specificity from species or subspecies to closely related species groups, subject to the amount of nucleotide sequence variation in the different organisms. A generic assay for all target species of Aspergillus, Penicillium and Paecilomyces was also developed and tested. Using a previously reported DNA extraction method, estimated conidia detection limits for target species ranged from less than one to several hundred per sample for the different assays. Conidia detection limits for non-target species were at least 1,000 fold higher in nearly all instances. The assays were used to analyze ten HVAC dust samples from different sources around the US. Total quantities of Aspergillus, Penicillium and Paecilomyces conidia in the samples, determined by the generic assay and the summed totals from the specific assays, were in general agreement, suggesting that all of the numerically dominant species in the samples were accounted for by the specific assays. The QPCR analyses detected from approximately 20 to 7500 fold higher levels of total target organisms than culture based enumerations on a commonly used growth medium in the different samples. QPCR analyses of these samples after spiking them with selected target organisms indicated that the enumeration results were within approximately a one-half log range of the expected values 95% of the time. Evidence is provided that the commonly used practices of enumerating Aspergillus and Penicillium as a single group or only by genus can be misleading in understanding the indoor populations of these organisms and their potential health risks.
