Advances in Rapid Microbiological Testing

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It can take up to two weeks or more to obtain results from traditional microbiological testing methods. Rapid, automated testing can reduce that time in half.

Conventional microbial analyses require extensive manual operations. In addition, the necessity for visual determination of the growth of microbial colonies leads to longer assay times. The result is a lengthy process that can take anywhere from three days to more than two weeks and that can dramatically impact production and commercialization times. Automated systems providing rapid results are helping to reduce that time, but the key to acceptance is staying consistent with the compendial method. Cynthia Challener, PhD, editor of the Pharmaceutical Sciences, Manufacturing & Marketplace Report, spoke with Julie Sperry, chief commercial officer of Rapid Micro Biosystems, to gain further insight into the application of rapid microbiological testing.

ApplicationPharmaceutical Sciences, Manufacturing & Marketplace Report: For what applications in the pharmaceutical industry is rapid microbiological testing appropriate and why? What benefits/advantages does it provide?

Sperry (Rapid Micro Biosystems): There are many areas where microbial analysis is critical in pharmaceutical manufacturing. Raw materials, work-in-process material, and final products all must undergo microbial testing. In addition, microbial monitoring of the manufacturing environment (i.e., personnel, surfaces, and air) is an ongoing process and critical to compliance. As a result, pharmaceutical quality-control laboratories often process hundreds, if not thousands, of tests per day, much of which involves manual manipulation of the assay plates for reading as well as data logging and other activities.

Rapid analysis with automation can, therefore, reduce the burden of manual plate counting and data entry on these laboratories and allow the workforce to be redeployed to address other important tasks. In addition, the level of human error can be reduced, and because the automation can provide the data immediately, decisions can be made quickly and definitive actions on process development issues and product releases can occur sooner.

Elements of a rapid microbiological systemPharmaceutical Sciences, Manufacturing & Marketplace Report: What are the critical factors that contribute to a successful rapid microbiological analysis system?

Sperry (Rapid Micro Biosystems): The most critical factor is the use of the established, or compendial, method, so that the analytical method doesn’t involve a major process change and can be validated without any need for extensive validation work.

Second, it is important that the method is nondestructive. If contamination is detected, then the microbes must be identified. Therefore, the test must be designed so that it doesn’t destroy or cause any change in the microbes. There are several ‘alternative’ technologies available, but many involve destruction of the microbes. In addition, many of these other methods don’t report the results in colony-forming units (CFUs), which is the standard unit for microbial testing. Therefore, the data have to be related to CFUs, which require validation of the data correlation and can introduce uncertainty.

Fluorescence-based systemsPharmaceutical Sciences, Manufacturing & Marketplace Report: How is it possible to develop an automated system that can meet these requirements?

Sperry (Rapid Micro Biosystems): The key is to use a growth-based method but [also to] develop a visual analysis system that can detect colony formation much sooner than is possible with the human eye. Our system is based on the natural auto-fluorescence of the microbes. Samples are prepared using media that is typically used for conventional analyses. A certain wavelength of light is shone on the sample, and if there is microbial contamination, the microbes auto-fluoresce. A very sensitive camera detects and captures this fluorescence.


To establish the growth rules for the software, extensive tests were conducted on many different types of microbes, including bacteria, molds and yeast, in order to develop reliable software that can detect colony growth and disregard non-growing debris, such as lysed cells or particulate components. The system was validated by comparing the results of automated determinations with determinations made using the conventional method.

The system takes readings every four hours and looks for differences. Often contamination can be seen within 8-12 hours, so in many cases, a problem can be identified after just two to three readings. The system then sends an alert message indicating that the colonies detected have exceeded a preset alert limit. With this type of automated detection system, it is possible to reduce the time needed for microbial analysis to about half of what is required for the conventional method.

Increasing applicabilityPharmaceutical Sciences, Manufacturing & Marketplace Report: How is automated microbiological testing being improved? What recent advances have been made?

Sperry (Rapid Micro Biosystems): One of the issues for some of our pharmaceutical customers is the need for separate systems for sterile-product testing. Others, on the other hand, want a system that can handle the whole range of different analyses, including sterility, bioburden, and environmental monitoring.

We have taken these customer requests very seriously and have developed a line of second-generation products, which will be released mid-year, that address these issues. One of the new instruments is specifically for high-throughput environmental monitoring and water/ bioburden analyses and is designed for high throughput.

The second new system is a specialized instrument for use in sterility-testing applications. This system includes the ability to test for both aerobic and anaerobic microbes. The system has three cassettes, one of which creates an anaerobic environment with a system sensor to detect and confirm that the cassette maintains an anaerobic atmosphere throughout the testing. The emphasis here is not only on time to results, but also proper sample preparation and handling.

The third new system is a multifunctional instrument designed to handle all of the different types of microbial analyses required in pharmaceutical manufacturing and whch can simultaneously run multiple analyses: sterility, environmental monitoring, water, or bioburden. This system is useful for smaller companies that can’t afford several individual instruments, but is also suitable for larger manufacturers that want to have the flexibility to validate a range of applications and then spin the validation out to their various sites.

Most importantly, the same growth-based method and detection technology is used across the product line. One added feature, though, is that these systems can be connected to a laboratory information-management system (LIMS) for improved sample tracking.

Lean processing Pharmaceutical Sciences, Manufacturing & Marketplace Report: What limitations remain with respect to rapid microbiological testing? What might be done to address these challenges?

Sperry (Rapid Micro Biosystems): There are several issues related to sample preparation and the subsequent identification testing that play a role in the turnaround time for the overall microbial testing process. Logistics, for example, can account for a significant amount of time and resource consumption. Often the testing is done in one location, but samples are collected elsewhere. Pharmaceutical companies can make efficiency gains with automated systems that can be operated in or closer to the manufacturing facility, particularly for environmental monitoring analyses. The capabilities of our new system facilitate this testing shift. Longer term, we are interested in finding ways to help our pharmaceutical customers speed up sample preparation and microbe identification so that they can maximize the increases in productivity and decision-making that rapid, automated microbial analysis systems can provide.