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Hygiene
The sampling head should be sterilised preferably by autoclave, but in the field disinfect with alcohol
or proprietary wipes. Wipes or alcohol can also be used to sterilise the MicroBio Box. In areas of
low bioaerosol levels, observe a disinfection regime between each sample. Always sample from
areas of lower contamination towards those of higher contamination, wash exposed skin and clothing
before sampling and avoid drinking, eating or smoking in the test area. All equipment should be
handled aseptically.
Temperature & Humidity
Make a note of these values at the time of each measurement. These are important factors in the
likely concentration and continuing viability of airborne microorganisms. For example, some bacteria
survival rates are 35 to 65 times higher at 80%RH compared to 40%RH.
Selection of Media
The agar media used in the 55mm contact plate or 90mm Petri dish should be chosen to suit the
organisms which are being monitored. For a wide range of bacteria, use tryptic soy agar (TSA),
casein soy peptone agar (CPSA) or nutrient agar (NA). There are other selective agars for more
specific micro-organisms.
Bengal agar (RBA).
After sampling with the MicroBio Samplers, the agar contact plates are incubated for specified times
and temperatures (typically 1-2 days, at 25 – 37°C) and the colonies which develop are counted. A
correction is applied to the colony count to allow for the possibility that two organisms going through
one sampling hole will result in only one colony growth being observed (positive hole correction).
From the corrected count and the sampling volume used, the number of colony forming units per
cubic metre (CFU/m
3
) can be determined.
Micro-organism
Bacteria:
Bacteria:
Bacteria:
Human Flora
Possible Pathogens
Environmental saprophytic
Thermophylic
Fungi:
Fungi:
Fungi:
Environmental saprophytes
Xerophylic
Media selected can be for general detection or selective to assist identification of organisms after
collection. Traditionally Malt Extract and Rose Bengal Agars are used for collection and counts of
fungi.
Various recipes are available from suppliers.
Peptone Agar and nutrient Agar are used. For both fungi and bacteria, various chemicals may be
added to the media to give selectivity.
June 2012
For fungi (yeasts and moulds), use malt extract agar (MEA) or rose
Agar Culture Medium
Blood Agar
Heart Infusion Agar
Soya bean-casein digest agar
(SCDA)
SCDA or R2A
EMB or Endo Agar
Malt Extract Agar(MEA)
Sabouraud Dextrose
Rose Bengal Agar (RBA)(with
streptomycin), Inhibitory Mould Agar
Malt Extract Agar with added NaCl,
sucrose or dichloran- glycerol
Typical media suitable for air sampling
MicroBio Operating Manual [P0001W006]
Incubation
Temperature
35 - 37°C
35 - 37°C
25 - 30°C
35 - 37°C
Room Temp
Room Temp
20 - 25°C
20 - 25°C
For bacteria, Tryptic Soy Agar, Casein Soy
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