The evaluation of airborne microorganisms is critical in the biopharmaceutical industry. For manufacturers that produce drugs
in an aseptic environment, cleanrooms must meet strict standards. Regulatory requirements such as the US Food and Drug Administration's
Guidance for Industry, Sterile Drug Products Produced by Aseptic Processing:
Current Good Manufacturing Practice and internal corporate policies require monitoring to verify that these standards are maintained. Cleanroom monitoring is
dependent upon reliable instruments that are suitable for sampling airborne contaminants in an aseptic environment. These
instruments must also be calibratable, portable, and easy to use
In this study, three active air samplers were evaluated for the collection of culturable airborne microorganisms. Bioaerosol
collection includes whole microorganisms as well as fragments, toxins, and particulate waste products from all varieties of
living things (1).
Materials and methods
Air samplers. The following air samplers were studied:
Table I: Estimates from the mixed-effects model of average recovery and standard deviation of the replicate measurements
(within day) of the airborne culturable bacteria concentration by air sampler in log10(cfu/ft3) units.
- The "SAS Super 180" sampler (Bioscience International, Rockville, MD) aspirates air at 180 L/min through a solid 304 stainless
steel sampling head with 219 precision-drilled holes positioned over the agar at a prescribed distance. After impaction, air
exits through an exhaust screen. The unit can accommodate either a standard 55/84-mm contact plate or a 90-mm standard Petri
dish below the sampling head. The sampler is fully programmable for features such as time between aspirations, volume of air
for each aspiration, and total air volume to be sampled.
- The "RCS Plus" (Biotest Diagnostics Corp., Denville, NJ) is a centrifugal impactor that draws air through the top of the instrument
at 50 L/min. The air exits the unit through exhaust ports. The sampler is designed for unidirectional airflow that minimizes
turbulence, thereby permitting sampling in laminar flow environments. The unit uses a proprietary air strip containing 34
wells each measuring ~1 cm2. The sample volume is programmable between 1 and 1000 L of air.
- The "Air Ideal" sampler (Bio Merieux Inc., Hazelwood, MO) is an air sampler based on air impaction. The air is aspirated by
a turbine at 100 L/min through a perforated surface. The holes form air jets that force the particles onto the agar placed
underneath the grid. The unit can accommodate either a 90-mm standard Petri dish or a 65/70-mm contact dish. The sample unit
is programmable for delay time and sample volumes.
Methods. When comparing various air samplers, the device properties of each piece of equipment must be taken into account (2). The
three air samplers that were evaluated have various flow rates. Therefore, all instruments were run for the same period of
time, not the same aspiration volumes. The same period of time was used to obtain each sample because of the varying population
of airborne organisms from minute to minute. All sampling was conducted indoors in a nonclassified laboratory area of nonmicrobiological
practices. The room's windows remained closed at least 24 h before measurements were taken. The opening of doors was minimal.
Sampling times were chosen at random throughout the day and over a period of several days.