The International Standard ISO 11133 describes the preparation, production, storage and performance testing of culture media and the performance testing of reagents used in ISO standards for food and water microbiology.
Tables of reference strains to be used for performance testing are included in this article.
The International Standard ISO 11133:2014 describes the preparation, production, storage and performance testing of culture media and the performance testing of reagents.
It contains information on how to prepare culture media in a consistent and reproducible way so that it is “fit for purpose” for the detection, enumeration and confirmation of target organisms specified in standards from two ISO committees for microbiology of the food chain and for microbiological water quality, respectively ISO/TC 34/SC 9 ‘Food products – Microbiology’ and ISO/TC 147/SC 4 ‘Water quality – Microbiological methods’. Microbiologists from these ISO committees are, as experts, working together in a joint Working Group (JWG 5) to expand and improve the content of ISO 11133 in order to further assure the quality of culture media and reagents. Some media and reagents from standards of ISO/TC 34/SC 5 ‘Food products – Milk and milk products’ are also included in ISO 11133.
Performance testing of culture media and reagents
In addition to information about the production of culture media, ISO 11133 describes performance testing procedures and defines the minimum acceptance criteria to achieve consistently reliable microbiological results. The control strains to be used for performance testing are specified in ISO 11133 (Annex E, F and K).
The tables linked here contain a complete list of culture media and reagents used in ISO food and water microbiology standards and some dairy standards with the names of control strains and their World Data Centre for Microorganisms (WDCM) collection numbers that should be used for testing the performance of culture media and reagents. The WDCM has compiled a catalogue of reference strains using a system of universal identifiers for strains recommended for use in quality assurance. It helps users find local sources of reference strains by citing all culture collections that hold that strain, their contact details and the individual collection’s unique reference number. Using this system also removes any commercial advantage obtained by citing the reference number of a specific culture collection.
The use of specific strains allows consistency between laboratories and facilitates the demonstration of differences between batches of media and between commercial and non-commercial producers. When more than one strain is listed for the same aspect of performance, the minimum strains to be used are indicated by the letter b. The list of strains in these tables will be updated at least annually.
Which performance testing of culture media to conduct?
ISO 11133 was published in 2014 and superseded all previous ISO publications and information on culture media. Amendment 1 (published in 2018) provides corrections and explanations whilst Amendment 2 (published in 2020) describes the performance testing of confirmation media and reagents. Since 2014, many standards have been published which contain their own specifications for performance testing of culture media used in the standard. These specifications are based on ISO 11133 but for technical reasons, they may include new control strains and/or revised specifications for the performance testing. All new and revised standards now specify the performance testing of culture media and reagents including the specification of control strains in the standard itself.
Any information on performance testing of culture media and reagents described in new or revised standards published since 2014 takes precedence over ISO 11133:2014.