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Swab & PCR sampling & tests for mold contamination in buildings: this article explains the use of mold test swabs to collect mold test samples to screen buildings for harmful indoor mold, followed by a discussion of PCR for mold identification and building mold screens. In this article series discuss the validity of nearly all of the popular mold testing methods currently in use, pointing out the strengths and weakness of each approach to mold sampling in the indoor environment, beginning with air sampling for airborne mold levels indoors.
Swab samples can be used to pull particles for microscopic
exam but destroy the identifying conidiophores and hyphae; They are more often
used to prepare cultures which have the shortcoming cited above. We make use of
swabs to sample for bacteriological contamination.
A sterile swab is wiped across a sampled surface, the inserted into a
sterile tube for mailing to a lab.
Swabs are processed in one of two ways:
Direct examination: The lab
can lift particles from the swab using tape or other methods to make a
direct particle examination similar to tape sampling above.
Culturing: The lab rolls the
swab across a culture plate to culture the sample for identification.
Shortcomings of swab sampling for mold:
Direct microscopic examination of mold swab samples:
determination of species by direct examination is often difficult as the
collection method destroys or fails to collect identifying structures such
as conidiophores and hyphae. "Rubbing" and possibly even
"rolling" the swab on a surface to collect a sample will often
destroy key structural components (the conidiophores and hyphal details)
which would have been more easily preserved using adhesive tape.
Culturing from mold swab samples (or
from mold tape samples): risks misidentification of the dominant species present and may
completely miss species which are present due to choice of culture media
and growing conditions. See Shortcomings of culturing for details.
Mold test swabs used to collect
particles from insulation, fabric, upholstery, carpets, may fail to
collect representative material as they only touch surface particles.
Vacuuming such surfaces is more representative of what particles are
aerosolized by human activity in a building.
Swabs are very effective for use in testing for bacteriological
contamination testing but in our opinion they are of less use in fungal work.
Polymerase chain reaction (PCR) can be used to identify
individual genera/species with good accuracy and fairly quickly. The method
requires costly equipment and is not available at most laboratories. Perhaps
more important is that the data base of PCR identification information is
limited to a small set of species compared with the wide range of
genera/species which occur.
At least one excellent national laboratory offers
this service for mold speciation. Depending on how rapidly technology drives
down the cost and how rapidly the identification data base is expanded, we suspect that this method will see increased use.
The limitations of PCR as a mold identification tool
are currently two: first, it is quite costly to perform per sample, and second,
it is excellent at identifying the presence or absence of a specific mold
you're looking for. It is less useful as a broad spectrum scan expected to pop
up with a result of what's present out of the 1.5 million possible candidates -
of which only a few are yet even in the PCR database.
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Craig Balchunas was an ASHI member, and a licensed New York home inspector and environmental and mold test inspector who previously practiced in Newburgh, NY.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention in Home Vegetable Gardens,"
Department of Plant Microbiology and Pathology,
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.