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Microbiological methods From February 2018 newsletter

Nine things to think about when choosing new microbiological methods

Numerous rapid tests are available for a range of microbial types. To choose the correct method that you need to carefully analyse what you do now and how you’d like to improve it, as well as answer some fundamental questions:

1. What do you need to test for? Pathogens, indicators, spoilage organisms? Do you need a rapid method for them all?

2. How many tests will you do per day? Do you have any constraints on staff numbers or laboratory space? Manual test require more staff input whereas fully automated systems can handle tens or hundreds of samples a day with minimal staff input.

3. How quickly do you want results? Faster results usually come at a cost.

4. What skill level is required for a new test? Some tests require skilled staff to carry out a test and interpret result; other “black box” type tests issue a final result from the entered sample.

5. What are you willing to spend on specialist equipment in order to do a new test? Some methods require a very large outlay on capital equipment - others may require very little.

6. What consumable cost are you willing to accept? Some of the more technical methods require relatively expensive consumables that drive up the cost per test. However, these tests may reduce product quarantine periods or the need for warehousing.

7. What are the servicing/calibration costs for the new method? Most methods will require the equipment to be serviced and calibrated at least annually, particularly if the method is part of an accredited test.

8. Will the method work? Will it give you accurate results? The best way to consider this is to look at whether the method is validated and certified by an independent third party.

9. Acceptability of the method - is the method allowed within legislation? Legislation or specifications may only allow a particular named method to be used or may not permit certain methods.

By taking a careful, structured approach, your laboratory can develop excellent new methods that help you to deliver high quality and fast test results.

Microbial method evaluation studies

Alternative methods used in food analysis must be shown to give comparable results to the relevant ISO reference method for the target microorganisms. The most comprehensive way to do this is to carry out a formal validation study to the requirements of ISO 16140. This is a series of analyses to test the performance of the alternative against the reference method.

We work with a number of different certification bodies – such as MicroVal, NorVal and AOAC - to provide an ISO 16140 certificate. If it is too early for full validation we can conduct a pre-validation study on your method to see whether it is likely to pass, or to show areas where further development is necessary.

If you are currently developing a new cultural or DNA based rapid method and wish to have the performance of your method evaluated then contact Dr Gail Betts -, +44(0)1386 842071

Contact: Dr Roy Betts
+44(0)1386 842075