At IFM, our philosophy is to develop testing protocols that reflect reality and usual behaviour. This approach helps provide a true reflection of a laboratory’s everyday performance. With this in mind, we always recommend.
- The use of real materials at concentrations and forms that closely imitate the types of materials that customers would normally submit. (In accordance with ISO/IEC 17043).
- A programmatic approach to support consistency over time and between analysts. Your laboratory’s performance should never be judged, based on a single proficiency program.
- Multiple samples because clients request multiple analyses Some are positive, some are negative for each of the targets, which means that analysts cannot give special handling to any particular sample.
- Mixed culture CRMs and references including non-type strains.
To examine the last point in more detail.
Many providers of quality products and services for microbiology exclusively use the type strains of target entities. Type strains are unambiguous. They are the ultimate example of a specific microbe which biochemically and genetically matches every test designed to identify them. Over time, however, the type strain adapts to reliably grow on the designated medium and is frequently cultured as the only organism on that control test.
As Ingrid Flemming points out.
“During the testing of “real life” materials, we can neither expect to find organisms adapted to being cultured, nor that a target is alone in a pure environment. Often wild target strains are present in a sample but they are vulnerable, damaged or more reluctant to grow. They are certainly never alone in a submitted sample. Exclusively using a type strain as a control therefore could give the scientist a false sense of security about the adequacy of their test system.
Finding an adapted strain alone, even at the correct level in the control test does not prove that the test system was optimal, nor that it would be impossible to have missed a wild entity fully capable of causing disease.”
Clearly no analyst, no laboratory nor any company would want to miss a wild entity that could cause disease if undetected. Testing exclusively with type strains leads to a false sense of security and an associated higher risk.
For this reason, IFM prefers to recommend the use of mixed culture CRMs and references including non-type strains.