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How it Works: Rapid Microbial Screening Systems

The traditional method of testing for microbial contamination has changed very little in the past 100 years. A sample of product is added to a growth medium in a plate or sample container.

by Charles River
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Problem: The traditional method of testing for microbial contamination has changed very little in the past 100 years. A sample of product is added to a growth medium in a plate or sample container. The samples are then put into a warm incubator and allowed to sit for several days to encourage the growth of any microorganisms that might be present. In a typical manufacturing lab, hundreds of plates are checked manually, day after day, until a specified number of days have passed without growth. Test times average 4 to 7 days for microbial limits and a minimum of 14 days for sterile products at each point of testing. Meanwhile, drums of raw ingredients, huge vats of in-process work and pallets of finished goods occupy valuable space in the warehouse and keep working capital tied up in inventory. Traditional methods are simply out of step with today’s more streamlined, modern manufacturing facilities, where products are within spec 99% of the time or more.

Solution: For materials and products typically free of bioburden, a simple absence/ presence primary screen offers the ideal solution for safely releasing the vast majority of products quickly. Rapid microbiological screening with adenylate kinase (AK) technology, such as the AKuScreen assay from Celsis Rapid Detection, combines the reliability of growth-based ATP, the gold standard of rapid testing, with a patented signal amplification that makes use of AK present in all living things.

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Because AK is an enzyme and not a metabolite, it can generate an almost unlimited supply of ATP when it is presented with an adequate supply of ADP. This strengthens the bioluminescence signal and, therefore, the assay’s sensitivity, shortening time to result.

Like the traditional method, sample preparation for the growth-based AKuScreen assay also starts by adding product samples to a medium and then incubating them. However, instead of waiting 4 to 7 days for microbial limits test results, the AKuScreen samples can be prepped, incubated and assayed all within 18 to 24 hours.

The rapid screening assay also reduces prep time and is more environmentally friendly: a single broth enrichment is typically used to detect bacteria, yeast and mould in all products. This reduces the amount of selective media that must be mixed and stored, as well as the various plates or jars needed to hold the different media for each replicate.

Whereas traditional samples are individually inspected for visual—and often very subjective—indicators of microbial growth, the Celsis screening system includes a sensitive luminometer with software that automatically controls the timing and volume of reagent injections. The instrument measures the light output of the AK-amplified ATP reaction, providing results in a colorcoded table or graphical view. The standardization provided by automation makes this a simple, yet state-of-the art approach that is easy to operate without the need for extensive training or an advanced degree. It can test up to 120 samples per hour, including a mix of product types and batches.

Definitive, objective results are generated within 24 hours for limits testing. It is this fast time to a negative result that is most critical: the “no to go” information needed to release products quickly. Such systems can be justified by the operational reductions in inventory and working capital as well as by the environmental savings in the lab. Celsis offers a financial and environmental impact assessment to help companies estimate these savings in advance.

When choosing a rapid method, be sure to evaluate the system to make sure it delivers on these criteria:

  1. Provides critical information when you need it, to keep your business running. Idled goods and materials cost money and take up space in the warehouse.
  2. Tests the majority of your products. Find a system that can test a full range of product types, including opaque, viscous, high or low pH, nonfilterable and highly pigmented materials.
  3. Environmentally friendly. Your system should enhance your lab’s sustainability initiative by using less energy and water and by reducing the amount of liquid, solid or hazardous waste you must dispose of daily.
  4. Easy to validate. By its nature, an absence/ presence test requires fewer steps to validate. But don’t stop there. Ask about the validation support and resources available from the manufacturer.
  5. Global support. Once you have a system in place, you won’t want to go back to the traditional method. So make sure the company has maintenance contracts, technical support and service available every place you need it, whenever you need it.

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