Mold & Bacteria Consulting Laboratories (MBL) is a leading commercial Canadian air quality testing laboratory in North America. Serving mainly the Canadian market, MBL specializes in lab analysis of air and surface samples for fungi (yeasts and mold) and bacteria. MBL is accredited by the Canadian Association for Laboratory Accreditation (CALA). Routine tests at MBL include:
- Bacteria testing: All environmental bacteria including coliforms testing, E. coli testing and Legionella testing
- Mold testing: Culturable air samples collected using BioCassette, Andersen, SAS, RCS, etc.
- Mold testing: Direct Microscopic Examination including tape, bulk, swab, water and soil samples
- Mold testing: Spore trap (or non-viable) samples such as Air-O-Cell, BioAire, and Micro5 cassettes, Allergenco, Burkard and BioSIS slides.
- Algae: Water samples, etc.
For more information on our air quality testing laboratory or for a complete list of microbiological tests performed at Mold & Bacteria Consulting Laboratories, please call our Ontario, Mississauga Office at 905-290-9101 or the British Columbia, Burnaby Office at 604-435-6555.
MBL, your indoor air quality testing laboratory.
The sample deposition trace is identified at lower magnification (10X or 20X) objective and spore counting is performed at a minimum magnification of X400. There has been a lot of debate as to what magnification should be used during identification and enumeration. Some analysts have recommended use of 100X oil immersion. However, it’s important to note that use of 100X objective with oil can be very messy and in most cases may not add quality to the results. In our opinion, the most important considerations when it comes to spore enumeration and identification are a good quality microscope and a well trained analyst.
In the past laboratories were using a variety of methods to analyze spore traps. This made comparison of results (and even terms used in the reports) difficult. The ASTM International has now released a new standard “Standard Test Method for Categorization and Quantification of Airborne Fungal Structures in an Inertial Impaction Sample by Optical Microscopy”. While this standard may not resolve all limitations of spore traps it will ensure that labs that use the standard analyze samples in a similar manner. The standard, however, may not improve the precision or accuracy of results, since, as it’s stated in the standard itself “…the detector in this method is the analyst, and therefore results are subjective, depending on the experience, training, qualification, and mental and optical fatigue of the analyst”.
Malt extract agar (MEA) is commonly used in indoor air quality surveys. MEA is a nutrient rich medium and has high water activity, which favors hydrophilic and fast growing species which may mask, inhibit or entirely suppress the growth of other fungi.
Viable air samples are often collected on agar media either in strips (if using Reuter Centrifugal Sampler) or in Petri-dishes for Andersen sampler. Unlike non-viable air sampling, detection and subsequent enumeration and identification of airborne fungal particulates collected on growth media depends on whether the spores and hyphal fragments are viable and whether the media used can support their growth into colonies. For this reason, colony counts are usually lower than spore counts. Even if all the fungal structures were viable, colony counts are likely to be lower than the spore/hyphal fragment counts because what is counted as a single colony could have developed from more than a single spore or hyphal fragment. In one study it was found that the ratios between the total fungal spores collected by the Burkard sampler and the viable fungi collected by the Andersen sampler ranged between 0.29 and 7.61.
Is Non-viable Fungal Air Sampling Alone Adequate? In most cases viable air sampling is only used in situations where identification of the moulds to species level is required. However, our observation in the lab seems to suggest use of spore traps alone may not be adequate for airborne fungal sampling. On many occasions we have recovered moulds in viable samples that were not observed in non-viable samples even when viable and non-viable samples were taken side by side. For example Chaetomium and Stachybotrys spores, which are fairly easy to identify from spore traps have appeared in viable samples, yet, they were not detected from the non-viable samples. We have also observed that although non-viable sampling gives higher counts than viable sampling in most cases, this is not always the case. There are many factors that can contribute to these “unexpected” results.
Since both non-viable and viable air sampling have limitations, using either method singly is not adequate. To obtain conclusive information on the level of contamination and the diversity of airborne fungi in a building, taking both viable and non-viable air samples is preferable. We recommend the Calgary Health Region’s protocol, “Fungal Air Testing, Investigation and Reporting Requirements for Residential Marihuana Grow Operations (Revised May 2006)”. With few exceptions, the protocol requires that fungal air sampling consist of both viable samples (e.g. RCS or similar) and non-viable samples (e.g., Air-O-Cell) taken side by side.