Blog and News


Automated Rapid Detection and the Power of the Positive

Posted by Admin User on July 10, 2012

Please welcome a guest poster to our blog. Anna Mills, our European Field Application Specialist, brings a wealth of knowledge and expertise in the area of rapid detection. 

Power of the positive

Microbial quality control in pharmaceutical manufacturing is all about zero.  The best news you can get about a sample is that it has a CFU count of 0.  It is counterintuitive to think that positive is bad, but anyone who has been involved in an investigation knows that a positive is the last think you want.  The big problem is the waiting game for that positive or negative result. 

The good old traditional test relies on a specific amount of incubation time before taking your sample and either reading get your result. Rapid Methods have accelerated this, but it is still a waiting game. Because of this even if you are getting an answer more quickly you are not necessarily aware as it happens.  What if you could learn that a sample has positive growth within hours, and could continue to let the sample incubate and grow to an endpoint where you could do identification?  That’s the power of the positive!

The Growth DirectTM Technology is a prime example of the power of the positive.  A sample is analyzed every few hours and can indentify growth quickly.  Compare that to the long wait in the traditional method.  Because Growth Direct™ includes automated analysis and alerting, positive results can be sent via email so you can take the quickest possible action in case of a failure in your lab.

The Growth Direct™ System uses agar cassettes to promote the growth of the bugs it means that growth of the colonies can continue in the Growth Direct’s built-in incubators until they are visible to the naked eye thus providing you with a purity plate so that you can ID the distinct colonies directly .    As an example, below is a small assortment of the bugs with their average time to detection in the traditional method versus the Growth Direct technology.

GrowthDirectTimeToDetectionWhat would it mean to you if you could pick up growth of certain bugs within the day?

What about slow growers? The difference between the Growth Direct™ time to positive and the traditional time to positive with slow growing organisms is often even more marked, for example we have found that Methylobacterium extorquens would grow (using a sterility turbidity format)in around 17.2 days ±3.2 days raising the question of how valid our compendial 14 day sterility test is.  However when we put this same organism onto the Growth Direct System we get a huge improvement in reading times, detecting it in 2.6 days ±0.7 days. 

We are excited to expand the power of the positive to sterility and environmental monitoring testing next year.  While a positive is bad, knowing about a positive sooner is definitely good.