Environmental monitoring (EM) is one of the critical parts of the overall microbial testing process performed in pharmaceutical manufacturing. With the traditional EM method, microbiologists use standard contact plates. Samples are captured, the contact plate is incubated and the number of colony-forming units are reported.
While the traditional environmental monitoring is a successful component of microbial testing of manufacturing, it is prone to handling and other potential errors. Because of the large number of samples typically associated with environmental monitoring, testing requires a great deal of time and effort from highly trained technicians – scarce resources in an environment that requires ever-greater efficiency and continual growth. A faster, more efficient and less error-prone alternative is the Growth DirectTM System, which automates and accelerates the compendial method using the same sample preparation techniques.
Recently, Dawn McIver, founder and president of MicroWorks, performed a study to compare the results obtained with traditional contact plates and the Growth DirectTM System's proprietary environmental monitoring cassettes. Ms. McIver has more than 18 years of experience in microbiology, and she has created the EM, cleaning and validation, equipment testing and training programs for a variety of pharmaceutical companies. She also authored the chapter, “Validation of Environmental Monitoring Methods,” published in Laboratory Validation, A Practitioner's Guide and Environmental Monitoring, both published by Davis Healthcare International Publishing.
Ms. McIver’s study tested both the Growth Direct Cassettes and contact plates using traditional techniques, and researchers counted colonies as they would during any other compendial test. The study compared the following attributes.
- Growth promotion
- Airborne viable bioburden
- Surface bioburden
- Naturally contaminated surfaces
- Inoculated surfaces
- Ability to neutralize common surface disinfectants
The conventional plates tested contained Tryptic Soy Agar with Lecithin and Polysorbate 80 (TSA w/LP80) utilized for surface sampling and airborne monitoring. The attributes of the Growth DirectTM System cassettes include:
- 0.45 micro pore size black mixed cellulose ester membrane as functional surface
- TSA w/LP80 media
- A external no-growth ring to prevent contamination from users
For comparison testing, both plates were serial incubated for seven days – four days at 20 to 25 degrees C and three days at 30 to 35 C. Colony counts after incubation revealed little difference between the traditional plates and Growth Direct Cassettes. One benefits of the Growth Direct Cassettes was that colonies, particularly molds and spreading colonies remained more compact, making them easier to count.
Growth promotion was performed on both the Growth Direct Cassettes and conventional TSA w/LP80 contact plates. The results of the growth promotion tests are outlined in the following chart. Correlation between the two was within acceptance criteria.
In the second part of this series, we'll discuss the results for airborne viable monitoring, naturally contaminated and inoculated surface bioburden and neutralization capability. Ms. McIver presented her results during an online seminar, and the results were recently published in the November/December Issue of American Pharmaceutical Review. If you want learn more about the study, watch the online seminar here.