Definitions of reference materials (RM) and certified reference materials (CRM) are given in EN-ISO International Standardisation Organisation (International Standardisation Organisation)(International Standardisation Organisation ) 17034:2016 ‘General requirements for the competence of reference material producers’ and in ISO Guide 30:2015 ‘Reference materials - Selected terms and definitions’.

Reference material (RM)
material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process

Note 1 to entry: Reference material is a generic term.

Note 2 to entry: Properties can be quantitative or qualitative, e.g. identity of substances or species.

Note 3 to entry: Uses may include the calibration of a measurement system, assessment of a measurement procedure, assigning values to other materials, and quality control.

Note 4 to entry: ISO/IEC Guide 99:2007 has an analogous definition, but restricts the term “measurement” to apply to quantitative values. However, Note 3 of the definition in ISO/IEC Guide 99:2007 specifically includes qualitative properties, called “nominal properties”.

[SOURCE: EN-ISO 17034:2016]

Certified reference material (CRM)
reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a reference material certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability

Note 1 to entry: The concept of value includes a nominal property or a qualitative attribute such as identity or sequence. Uncertainties for such attributes may be expressed as probabilities or levels of confidence.

Note 2 to entry: Metrologically valid procedures for the production and certification of reference materials are given in, among others, ISO Guide 35.

Note 3 to entry: ISO Guide 31 gives guidance on the contents of reference material certificates.

Note 4 to entry: ISO/IEC Guide 99:2007 has an analogous definition.

[SOURCE: EN-ISO 17034:2016] 

Development of (certified) reference materials

From 1986 up to 1995, the Microbiological Laboratory for Health Protection (MGB) of the Dutch National Institute for Public Health and the Environment (RIVM Rijksinstituut voor Volksgezondheid en Milieu (Rijksinstituut voor Volksgezondheid en Milieu)(Rijksinstituut voor Volksgezondheid en Milieu)) led EU Europese unie (Europese unie)(Europese unie) funded projects on the development and certification of microbiological reference materials. After their development, the non-certified reference materials were produced by the Foundation affiliated to the RIVM until 2003. The experiences and knowledge obtained from the development and production of these (C)RMs have been applied in preparing reference materials for use as standard samples in the Proficiency Tests of the EURL European Union Reference Laboratory (European Union Reference Laboratory)(European Union Reference Laboratory )-Salmonella up to 2010.

Availability of microbiological (certified) reference materials

Microbiological reference materials (certified and non-certified) are produced in different formats by several national and international organisations. For example: reference strains from culture collections, reference materials containing a set number of one or more culturable organism(s) or reference materials containing genomic DNA of a microorganism. 
For information, the details of some (C)RM producers are given below. 

Mind that this list is not exhaustive and that the information is given for the convenience of the users and does not constitute an endorsement by the EURL-Salmonella

Culture collections

World Data Centre for Microorganisms (WDCM)
Many national and international culture collections exist which preserve, authenticated microbial strains. These collections are developed, managed and maintained in accordance with internationally recognized quality standards.
Some cultures representing the same strain are available at different culture collections, obtaining a unique culture collection number at each culture collection. Some of these strains are listed in the catalogue of the World Data Centre for Microorganisms (WDCM), especially the reference strains listed in EN-ISO 11133:2014 (‘Microbiology of food, animal feed and water - Preparation, production, storage and performance testing of culture media’) for the quality control of culture media. 
For example: In EN-ISO 11133:2014 and EN-ISO 6579-1:2017 for the performance testing of MSRV agar, the use of Salmonella Typhimurium WDCM 00031 or Salmonella Enteritidis WDCM 00030 is prescribed. In the WDCM Reference strain catalogue it can be found that Salmonella Typhimurium WDCM 00031 is available at 13 different culture collections and Salmonella Enteritidis WDCM 00030 is available at 9 different culture collections. The different culture collection numbers represent the same strain for one WDCM number. E.g. WDCM 00031 is available as ATCC 14028, but also as NCTC 12023, or CIP 104115. Whereas WDCM 00030 is available as ATCC 13076, but also as NCTC 12694.

More information on the World Data Centre for Microorganisms (WDCM) can be found at: link) 

Examples of culture collections:

Belgian Co-ordinated Collections of Micro-organsims (BCCM)
Belspo, Belgium link) 

Czech Collection of Microorganisms (CCM)
Masaryk University, Czech Republic link)

Collection de l’Institut Pasteur (CIP)
Institute Pasteur, France…(externe link)

German Collection of Microorganisms and Cell Cultures (DSMZ)
Leibniz Institute, Germany link) 

The Netherlands Culture Collection of Bacteria (NCCB)
Westerdijk Fungal biodiversity Institute, The Netherlands link) 

Spanish Type Culture Collection (CECT)
University of Valencia, Spain…(externe link) 

National Collection of Type Cultures (NCTC) for bacteria
Public Health England, United Kingdom link)

American Type Culture Collection (ATCC)
LGC Standards, USA link) 

Microbiological (certified) reference materials

EC-Joint Research Centre (JRC)
The European Commission’s Joint Research Centre (JRC) in Geel, Belgium develops and produces (certified) reference materials and most of the reference material projects are performed in collaboration with various external institutions. Since 2004, JRC is accredited according to ISO 17034 and ISO/IEC 17025. The catalogue of JRC also contains a (small) list of certified microbiological reference materials.

More information, as well as the online Certified Reference Materials catalogue can be found at: link) 

Examples of producers of microbiological (certified) reference materials:

BIOBALL® Reference Materials
Biomerieux, France…(externe link)

Vitroids™ and LENTICULE® discs Reference Materials
Sigma-Aldrich/ Merck, Germany…(externe link)

Biosisto (Certified) Reference Materials
The Netherlands link)

ielab Reference Materials
Spain…(externe link)

easi-tabTM Reference Materials
LGC Standards, United Kingdom