ISO 11133:2014 Microbiology of food, animal feed and water — Preparation, production, storage and performance testing of culture media

The ISO 11133:2014 standard “Microbiology of food, animal feed and water − Preparation, production, storage and performance testing of culture media”, replaces previous standards and aims at enhancing the reliability of microbiological analyses by standardizing the quality and performance testing of culture media dedicated to microbiological analyses of food and water.

These requirements are applicable to all categories of culture media prepared for use in laboratories performing microbiological analyses.

This International Standard also sets criteria and describes methods for the performance testing of culture media. This International Standard applies to producers such as:
- commercial bodies producing and/or distributing ready-to-use or semi-finished reconstituted or dehydrated media;
- non-commercial bodies supplying media to third parties;
- microbiological laboratories preparing culture media for their own use.

In May 2014, the International Organization for Standardization (ISO) published the revised EN ISO 11133, which is now a full standard and as such mandatory for all accredited laboratories that perform microbiological testing of food, animal feed or water using culture media. It has been completely restructured, clarifying procedures and drawing a clear line between the responsibilities of the laboratories and the manufacturers/suppliers of culture media. The ultimate aim of the new standard is to further improve the safety of the food and beverage products we consume.

1. What is the new standard?

The new EN ISO 11133:2014 Quality-assured culture media for food and water testing to enhance consumer safety The one-part EN ISO 11133:2014, titled “Microbiology of food, animal feed and water – preparation, production, storage and performance testing of culture media”, was compiled by a joint ISO working group from food and water standardization. It applies to culture media intended for the microbiological analysis of food for human consumption, animal feed and samples from the manufacturing environment of such products, as well as of all kinds of water for consumption or use in food production. It covers all culture media formats, ranging from dehydrated and ready-to-use media for classical microbiological methods to media for alternative testing techniques.

2. What are the objectives of the standard?

There are two guiding principles in this regulation: Media preparation and performance testing. For example, very practical guidance is provided for the testing of water quality for media preparation, pH adjustments, storage of prepared plates, tubes and bottles.

The second guiding principle is that performance testing conditions should resemble the intended sample testing conditions as closely as possible, leading to more accurate and meaningful results. As a consequence, culture media for quantitative testing must now be tested quantitatively, and those used in conjunction with membrane filters must be tested in combination with these filters. Another objective is to specify the requirements in more detail and describe the practical aspects. Step-by-step instructions, complemented by flow charts, are provided for performing and evaluating performance tests. The standard contains comprehensive tables for the specifications for most culture media, not only for food but now for water microbiology as well.

3. What has been included in the new standard?

In addition to the medium’s target microorganism and the relevant ISO standard, these tables show each medium’s functions to be tested (productivity, selectivity, specificity), the appropriate control strains for these functions, including their World Data Centre for Microorganisms (WDCM) numbers, as well as the test criteria and/or characteristic reactions and other practical information. EN ISO 11133 now also contains hands-on, detailed instructions for the maintenance of microbial strains as well as the preparation and standardization of working cultures and inoculation suspensions. The standard specifies the optimal number of colony forming units (cfu) per plate or membrane filter and describes how productivity ratios and limits are determined.

4. What does this change mean for labs?

An ever-increasing number of laboratories source their culture media from suppliers to simplify their workflows and ensure high quality and batch-to-batch consistency of the media they use. EN ISO 11133:2014 takes account of this development by stipulating requirements not only for laboratories that prepare their media in-house but also for manufacturers. With a clear line drawn between the quality assurance responsibilities of users and suppliers, lab managers can now reliably assess which duties and responsibilities no longer apply when they decide to procure culture media. For labs that produce their own culture media, it is usually sufficient to test each batch with a single test strain named in the standard, whereas manufacturers are expected to perform tests using several microorganisms. However, both labs must meet the specified productivity and selectivity to a level as described for each test organism.

5. Are extensive tests required by all labs?

For all ISO 11133:2014 compliant culture media they provide, suppliers need to conduct rigorous qualitative and/or quantitative testing. However, ready-to-use media allow laboratories to rely on the performance tests that the manufacturer conducts as long as the transport conditions are observed and the manufacturer’s QC test is performed according to the requirements of EN ISO 11133. The end user needs to make sure that testing was performed according to the requirements of the standard. A supporting document that the manufacturer provides to the end user is the quality control certificate. It discloses the test organisms used, the inoculation levels, the acceptance criteria of the performance tests and the test results.

Each production lot of Liofilchem media is accurately tested for growth promotion, sterility and reproducibility with a schedule that includes the microbial strains indicated in the standard, therefore simplifying the amount of validation customers have to do in their own laboratories on each lot of ready-to-use media.

The QC certificates have been progressively updated and contain the statement “Tested according to EN ISO 11133”, to show and guarantee reliable results and batch-to-batch media consistency.

As Liofilchem manufactures ready-to-use culture media using its own dehydrated culture media, its stringent system of procedures for conformity to the technical specifications and control testing can be followed through the entire production process making full traceability easier.

The full compliance of Liofilchem to ISO 11133:2014 standard, in addition to the ISO 9001 and ISO 13485 certifications, reinforces its position as one of the world class leading manufacturers of diagnostics for microbiology.