Monitoring Of Bioaerosols - Cantium Scientific MicroBio MB2 Operating Manual

Indoor areas: Many indoor areas are associated with bioaerosol problems.
In all food processing plants, hygiene requires that levels of airborne micro-
organisms are kept as low as possible. Hospitals and healthcare facilities are
not only sources of a variety of organisms, but require that patients are not
exposed to any of them. The presence of undesirable bioaerosols is often
associated with sick building syndrome, being one of a number of factors
which contribute to building related illness.

Monitoring of Bioaerosols

Although the use of simple settle plates can be used for collection of bacteria
and fungal spores, it can never give a quantitative determination. This
passive technique will also fail to enumerate very small particles such as
bacteria, which will remain suspended.
The simplest quantitative method of monitoring is to use sieve impactors,
which collect bacteria and fungal spores from air flowing at 100 litres per
minute through a series of air inlets, onto an agar filled 55 mm contact plate
or 90 mm Petri dish, up to a volume of 2,000 litres.
The agar media used 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) and
nutrient agar (NA). There are other selective
agars for more specific micro-organisms. For
fungi (yeasts and moulds) use is made of malt
extract agar (MEA) or rose bengal agar (RBA).
After sampling with the MicroBio samplers, the
agar plates are incubated for specified times
and temperatures (typically 1 to 2 days at 25 to
37 deg C) and the colonies which develop are
counted.
A correction is applied to the 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). This is determined from
tables or using the MicroBio PC Reporter software supplied with all MicroBio
samplers. From the corrected count and the sampling volume used, the
number of colony forming units per cubic metre (CFU/m3) can be
determined.
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