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

BioVigilant has developed a nonculture-based instantaneous microbial detection (IMD-A) system based on optical fluorescence sensor technology. The IMD-A system analyzes the quantity and size of biological particles in environmental air and simultaneously determines whether each particle is inert or biologic, all in real time.3 The IMD-A consists of three components: 1) an optical assembly to measure individual particle size, 2) a concurrent optical detector to detect a UV-laser-induced fluorescence signal from metabolites in microbial cells and spores, and 3) an algorithm for differentiating airborne microbes from inert dust particles. The optical assembly uses the Mie scattering detection scheme to accurately measure airborne particles with sizes ranging from 0.5–20 m. Exploiting the Mie scattering detection scheme enables the use of ultraviolet (UV) light illumination to concurrently examine each particle for the presence of nicotinamide adenine dinucleotide (NADH) and riboflavin, which are necessary metabolic intermediates of living organisms, including bacteria and fungi. These metabolites are excited by the UV photon energy and subsequently by autofluoresce, which is detected by the sensor. Although the IMD-A cannot identify the genus or species of microbes, it can instantaneously determine the size of each airborne particle and whether it is biologic or inert.

Table 2. Statistical evaluation of 1-m3 microbial barrier test chamber data from the IMD-A and an Anderson air sampler—Staphylococcus aureus (vegetative cells)
The overall objective of this study was to evaluate the IMD-A system in controlled and pharmaceutical cleanroom environments by comparing it with other microbial air monitoring methods. Specifically, we set out to do the following:

1. Evaluate BioVigilant's instantaneous microbial detection (IMD-A) system in a microbial barrier test chamber (1 m3 and 150 m3) in a microbial challenge side-by-side with conventional (Anderson air and air impingement) air-sampling methods

2. Evaluate the IMD-A for use in cleanroom Class E (ISO 9), Class D (ISO 8, Class 100,000 at operational and static), Class C (ISO 7/8, Class 10,000 at static and 100,000 at operational), and A (Class 100, ISO 5) environments at the Bayer Berkeley site by running the IMD-A side-by-side with conventional (SAS) air sampling methods

3. Compare the microbial recoveries in environmental air using the IMD-A with those obtained using ScanRDI.

Note that classified areas mentioned above were monitored using areas that were in control, but not in use for manufacturing.


The 1-m3 microbial barrier test chamber challenge study was performed at Nelson Laboratories (Salt Lake City, UT). In the first study, cultures of Bacillus atropheus spores were inoculated onto soybean casein digest agar (SCDA) and incubated for 2–7 days at 30–35 C. The cultures were harvested in sterile water and the suspension was subjected to heat shock at 80–85 C for 10 minutes to destroy vegetative cells. The titers of the spore suspensions were determined by serial dilution and plating onto SCDA, then adjusted to yield concentrations of 104–108 cfu/mL.

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