Each CRM is supplied with a certificate providing metrological traceability, the expected level of the target organism(s), and the associated measurement uncertainty, helping you ensure reliable and consistent results.

Storage

Upon receipt, it is crucial to store the products in a dark and cool place (3 - 5 °C).
Maintaining this condition is necessary for the material to retain the level of target organisms until the expiry date.

Dilution instructions

The certificate includes information for performing primary dilution of the samples, detailed in Instructions for Use.

Expiry dates

There are two expiry dates specified:

• Product Expiry:
  This marks the date when the reference material (freeze dried or powder) expires.
• Certificate Expiry:
  This is the date when the certificate with specified levels of target organisms expires.

Recertification

The certificate indicates whether the material will be recertified (resulting in a new certificate), or if it is final and expires simultaneously with the products shelf life. New certificates are issued at regular intervals until the product’s shelf life expires. Upon certificate expiry, a new one will be provided if needed.

Assigned value

This represents the expected level of the target organism, along with low and high limits, indicating 3 standard deviations.

Designation

Note the designation on the certificate. Freeze-dried microorganisms in glass vials specify the level per vial (CFU/vial) while the powder samples indicate levels as CFU/g.

In detection tests, the enrichment broth is typically inoculated with a predetermined concentration of the target organism sourced from the Certified Reference Material (CRM). This spiked sample undergoes the complete analytical process, it simultaneously checks the enrichment broth and the incubator, a PCR step or any other rapid method, if used, and selective agars. The certified reference material is accompanied by a certificate containing crucial information regarding its composition.

An example of the level of target organisms from a certificate:

The quantity in this certificate is given in CFU/g. If you intend to verify the method for detecting Salmonella spp., follow these steps: Accurately weigh the material (10 grams) and add diluent in buffered peptone water. While the standard procedure involves a 1/10 dilution, you can adjust the dilution ratio to suit your specific requirements. The expected level (assigned value) according to this certificate is 2700 CFU/g of Salmonella spp., with a range spanning from 1100 to 4900 CFU/g. If diluted at a 1/10 ratio, the expected level becomes 270 CFU/ml with a range of 110 to 490 CFU/ml. By inoculating your control sample with 100 µl of this solution, you will have an approximate level of 27 CFU. Adjust the level as necessary and adhere to your standard procedure. Inoculate the enrichment broth that fits your target organism. The same primary dilution may be used for both L. monocytogenes and Salmonella spp.

In summary: Check the certificate’s expiry date. Review the expected level and tolerance limits. Determine the desired inoculation level and adjust the dilution accordingly.

The material can also be used to spike a chosen matrix. This is beneficial for validating/verifying a new method or verifying an existing one. Alternatively, it can be used alongside the analysis of a customer's sample. This proves especially valuable when the sample material is unfamiliar to the laboratory or where, for some reason, there is uncertainty whether the target organism can be recovered from the particular matrix.

In this process, one of the customer's samples undergoes standard analysis, while the other is spiked with the desired level of CRM. Both analyses are carried out simultaneously. This approach ensures a potential recovery of the target organism from this specific material, accounting for its inherent properties and natural flora. Unknown sample materials may contain competing flora and/or unidentified inhibitory substances, and spiking provides insights into these factors. 

Example of simulated water sample preparation

The vial contains, for example, 4000 CFU/vial of P. aeruginosa, this represents approximately 400 CFU/ml when when diluted 1/10.

If 1 ml of this solution is added to 1 liter of water, the expected level will be around 40 CFU when filtering a 100 ml water sample. If a 10 ml water sample is filtered, approximately 4 CFU will be obtained.

Choose appropriate volume from the vial to achieve the desired concentration.

Example of simulated food sample preparation

The vial contains, for example, 2900 CFU/vial of C. perfringens, this represents approximately 290 CFU/ml when diluted 1/10.

A direct plating from this primary dilution can be perfomed. Pour plating 1 ml of the resuscitated material into TSC agar will result in an overgrown dish of 290 CFU. An expected level of approximately 29 CFU will be obtained by plating 0,1 ml of the material. Alternatively, the same expected level of 29 CFU can be obtained from 1 ml of a -2 dilution.

Choose appropriate volume from the vial to achieve the desired concentration.

Example simulated food sample preparation with matrix

The vial contains, for example, 25 000 CFU/vial of E. coli, this represents approximately 2 500 CFU/ml when diluted 1/10. 

Weigh 10 grams of the selected food matrix sample. Combine 90 ml of dilution fluid and 1 ml of resuscitated material and homogenize. Pour plate 1 ml from this primary dilution into TSC agar, the expected level will be approximately 29 CFU/g.

Choose appropriate volume from the vial to achieve the desired concentration.

Download instruction:

Preparation of CRM Samples in vial format

Download instruction:

Preparation Of CRM Samples In Powder Format