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Environmental Analysis

Bulk sample, quantitative fungal culture [FC-B]

Published: July 8th, 2009

Revised: January 29th, 2019

Solid or so-called “bulk” materials, such as wood, carpet, and other insoluble, solid items, can be evaluated by quantitative fungal culture to determine their culturable fungal content. All or a portion of the specimen is weighed, placed in a buffer solution and vigorously agitated to suspend adherent spores or vegetative hyphae. Aliquots of suspension are plated, the plates are incubated, and resulting colonies are identified and counted.

Although this methodology may seem straightforward, (indeed, in the laboratory it is a relatively simple procedure), the test is extremely difficult to standardize. This is because the surface area to volume ratios and densities of materials vary considerably, and most fungal colonization is likely to be restricted to the surface of the material. Although similarly sized coupons of comparable materials could be reasonably compared using this test, the method does not provide meaningful, information in an absolute sense on the fungal content a sample. Still, there remain a few indications for this test. For example, this approach may be informative where there is an interest to compare a capsulesset of identical or nearly identical objects based on the concentration of culturable fungi recovered. Such an item might be an industrial part, an herbal supplement or a biomedical device, where items from the same or different lots are compared. This test is generally not useful in indoor environmental investigations.

Field collection method

There is no specific field collection method for this test, per se. Items to be tested should be placed individually in a labeled tube or envelope to which a label containing all relevant sample information has been affixed. The test is semi-destructive, since depending on the size of the specimen, we may need to dissect portions of it in the laboratory to obtain a suitably sized coupon for analysis.

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Results reporting

Results of this test are reported in Colony Forming Units per milligram of material (CFU/mg), and broken out according to species, species-group or genus observed (the identification level depends on the taxon in question).