In March 2014, the International Organization for Standardization (ISO) introduced the revised EN ISO 11133:2014, which is now a mandatory standard for all accredited laboratories that perform microbiological testing of food, animal feed, or water using culture media. The standard was compiled by a joint ISO working group from food and water standardization and titled “Microbiology of food, animal feed and water—preparation, production, storage, and performance testing of culture media.” EN ISO 11133:2014 defines the preparation and quality control of culture media, the requirements of which are applicable to all categories of culture media prepared for use in laboratories performing microbiological analyses. This new standard replaces EN ISO TS 11133-1:2009 (Preparation of culture media), EN ISO TS 11133-2:2003 (Performance testing of culture media, both for food and feed microbiology), and ISO 9998:1991 (Requirements for microbiological media for water testing).
EN ISO 11133:2014 applies to any commercial or non-commercial entity that is producing and/or distributing 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 water for consumption or use in food production. The new standard includes all types of culture media, ranging from dehydrated to ready-to-use media for classical to alternative microbiological testing methods.
All European Union (EU) countries are adopting EN ISO 11133:2014 and the standard is currently published in French and German. In addition, all accreditation bodies worldwide recognize EN ISO 11133:2014 because it is now a full EN ISO standard.
An EN ISO 11133:2014 Overview
EN ISO 11133:2014 covers requirements for the preparation, production, storage, and performance testing of culture media. Under the new standard, all conditions for performance testing should resemble the intended sample testing conditions as closely as possible in order to provide the most accurate and meaningful results. For example, culture media for quantitative testing must now be tested quantitatively, and media used in conjunction with membrane filters must now be tested in combination with these membrane filters. The requirements for performance testing are specified in detail, which includes step-by-step instructions and flowcharts for performing and evaluating performance tests.
The standard provides comprehensive specification tables for most culture media for both food and water microbiology. These tables include the medium’s target microorganism; relevant ISO standard; each medium’s function to be tested (productivity, selectivity, specificity); the appropriate control strains for each medium’s function, including their World Data Centre for Microorganisms numbers, and; test criteria and/or characteristic reactions and other practical information (Table 1).
EN ISO 11133:2014 contains detailed instructions for the maintenance of microbial strains and the preparation and standardization of working cultures and inoculation suspensions. It specifies the optimal number of colony forming units, or CFU, per plate or membrane filter and describes how productivity ratios and limits are to be determined.
Quality Assurance Responsibilities
Many laboratories source their culture media from suppliers both to streamline their workflows and to ensure high quality and batch-to-batch consistency. EN ISO 11133:2014 takes into account the ever-increasing number of laboratories sourcing their culture media from suppliers by stipulating quality assurance requirements not only for laboratories that continue to prepare their media in-house, but also for manufacturers of culture media. With a clear line drawn between the responsibilities of users and suppliers, laboratory managers can now reliably evaluate which duties and responsibilities will transfer to the manufacturer when they make the decision to procure culture media from a supplier.