Bioaerosol sampling according the Method 0800 – NIOSH USA
Glossary: Bacteria, Building reservoir, Complaint area, Control areas, Culturable micro-organisms, Fungi, Genus, Heterotrophyic bacteria, Mesophilic bacteria, NIOSH, National Institute for Occupational Safety and Health, Noncomplaint area, Outdoor, Species, Taxa, Thermophilic actinomycetes, Xerophilic mould,
▪ NIOSH (National Institute for Occupational Safety and Health) METHOD
0800, Issue 1, 15 January 1998.
▪ PURPOSE
Identification of culturable micro-organisms and assessment of possible proliferation and dissemination of bacteria or fungi from building reservoirs.
▪ FIELD EQUIPMENT
1. Samplers:
Andersen type impactor like “SAS ” or “DUO-SAS” for fungi, mesophilic bacteria, and thermophilic actinomycetes. The “DUO-SAS” air sampler can be used with metal autoclavable aspirating heads or “Daily-Head” disposable, plastic, officially sterile certified aspirating heads.
The “DUO-SAS-360” portable microbiological air sampler is the ideal instrument because two different media for two different micro-organisms can be tested at the same time and it is a battery operated sampler that doesn’t need a vacuum pump.
Air flow controller like “Pyramid”.
Plates: Standard 90 mm Petri dish or Contact Plate (RODAC)
2. Sampling media:
a. Malt Extract Agar (MEA) for fungi.
b. Trypticase Soy Agar (TSA) for mesophilic bacteria and thermophilic actinomycetes.
NOTE. Other media may be used, if appropriate, e.g.: DG18 for xerophilic moulds, R2A agar for heterotrophic bacteria, and Rose Bengal Agar for slow growing fungi such Stachybotrys.
3. The air flow rate of the sampler should meet manufacturer’s flow specification (e.g.: 28,3 litres per minute or 100 litres per minute, or 180 litres per minute).
4. Cotton gauze pad
5. Rubbing alcohol, sterile 70% isopropanol.
6. “Penguin” Cooled transfer system for keeping cool during shipment e.g.:
NOTE. Keep samples cool, but protect from freezing.
▪ SAMPLING STRATEGY
1. Select at least 3 sites, one each to represent complaint area, a noncompliant area (otherwise as similar as possible to complaint area), and outdoors.
2. In turn, at each site, sample simultaneously for fungi, mesophilic bacteria, and thermophilic actinomycetes. Typical sampling time is ten minutes. Before moving to the next site, repeat twice to obtain triplicate, consecutives samples.
3. Load and immediately unload one set of sampling media in each sampler to serve as field blanks.
4. Collect another complete set of samples and blanks on the next day.
▪ SAMPLING
1. Calibrate each sampler (this operation should be officially performed each 6-12 months at the producer or distributor premises and non-officially every week with the “Pyramid” System).
2. Before each run, carefully and thoroughly wipe each sampler stage with rubbing alcohol. Allow to dry. Make sure that air passages in the aspiration head are not blocked.
3. Load plate with sampling media into aspirating chamber of the sampler, remove cover from the plate, apply the disinfected aspirating metal or sterile plastic head.
NOTE. Take special care to prevent contamination of media during loading and unloading. Do not touch agar surface.
4. Sample at known preset flow for an accurately known time, e.g.: 10 minutes (in heavily contaminated areas, a shorter sampling time may be necessary). e.g.:If the air flow is 100 litres per minute, 1.000 litres of air are collected in 10 minutes, 500 litres in 5 minutes, 200 litres in two minutes. If the air flow is 180 litres per minute, 1.000 litres of air are collected in about 6 minutes.
5. Unscrew the aspirating head, replace cover on sampling media, unload the plate, and pack securely for shipment (plates should be media side up).
▪ SHIPPING
Keep collected samples and blanks cool (not necessary ice-cold) and ship as quickly as possible to a laboratory for enumeration and identification.
▪ ANALYSIS
Mesophilic bacteria end thermophilic actinonmycetes are usually identified to species and fungi usually identified to genus. Interpretation is subjective and based on total numbers and rank orders of taxa in complaint area compared with control areas.
