Evaluation of an Instantaneous Microbial Detection System in Controlled and Cleanroom Environments - - BioPharm International


Evaluation of an Instantaneous Microbial Detection System in Controlled and Cleanroom Environments

BioPharm International
Volume 21, Issue 9

However, since the IMD-A can simultaneously detect whether a particle is biological or not and determine its size, any potential microbial aggregates larger than individual cells can be readily flagged by the IMD-A. The lower microbial recoveries from the Anderson air samplers compared with the IMD-A or the AGI are not unexpected, since centrifugal, filtration, and impinger methods are thought to provide better recoveries and suggested to be more suitable methods for microbiological air monitoring than are impaction methods such as Anderson air samplers.4 Additionally, the desiccation effects5 created during impaction can limit the recovery of microorganisms on media plates. It is also well recognized that microorganisms in air may remain viable but lose the ability to form colony forming units, so that culture-based methods may underestimate microbial populations in environmental air.6

In the classified cleanroom environments examined, microbial recoveries in environmental air as assessed by the IMD-A were substantially higher than those from the SAS air sampler, which recovers microorganisms by the impaction method. Reasonable correlation of microbial recoveries were observed between the IMD-A and the SAS air sampler in cleanroom environments (Figures 3, 4, and 5) Class E, Class, D, and Class C (r2 = 0.51, 0.42, and 0.32, respectively). Microbial recoveries from the IMD-A were approximately two orders of magnitude higher than those observed from the culture-based SAS method. Because of its slower flow rate, the IMD-A was operated for a longer time than the SAS air sampler. The higher recoveries may be partly explained by the fact that the IMD-A device could have captured microorganisms from activities in the cleanrooms subsequent to the end time of testing using SAS.

Figure 5
Additionally, in natural environments, microorganisms can exist in viable, nonviable, or viable but nonculturable (VBNC) states, the latter of which is the predominant form.7–9 This is partly due to the fact that culture-based methods are very selective in their ability to recover microorganisms that often exist in symbiotic or syntrophic relationships in natural environments. There is little or no published information available about the VBNC phenomenon as it occurs in controlled cleanroom environments. However, it is quite conceivable that cleanroom environments could have substantial levels of nonviable microorganisms, because of the controlled environmental conditions in cleanroom environments that could be captured by the IMD-A, especially if the microorganisms recently lost their viability but still have substantial pools of metabolic cofactors such as NADH that persist and are detected by the IMD-A sensor.

Figure 6
Results for the controlled microbial barrier test chamber, the ScanRDI study, and the cleanroom environment studies suggest that the IMD-A has the potential to provide a reliable evaluation of the microbial populations in environmental air and can detect variations in environmental microbial counts in cleanroom environments that are usually detected by conventional air sampling methods. While the microbial counts from the environmental air detected by the IMD-A in cleanroom environments were substantially higher than the conventional air sampling method, the ability of the IMD-A to simultaneously detect microorganisms in real time will prove the IMD-A to be a valuable analytical tool once its baseline for cleanroom environments is established.


The IMD-A system can be valuable in monitoring environmental air in pharmaceutical manufacturing areas because of its ability to evaluate microbial quality of the environmental air in real time. There are several areas where we believe the IMD-A has potential immediate benefits:

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