ISO 11133 – Evaluation of Microbiological Performance Testing in Quality Control of Culture Media

Introduction: The International Standard ISO 11133 “Microbiology of food, animal feed and water – Preparation, production, storage and performance testing of culture media” is currently under revision and is planned to be published mid 2014. The revised standard ISO FDIS 11133 describes all methods for the routine control of culture media. It specifies the requirements and acceptance criteria for the performance testing for the most culture media given by International Standards for food and water microbiology for the lab user and manufacturers.

Purpose: The purposes of this current study were to perform and evaluate the performance testing of culture media including the acceptance criteria given by the revised standard ISO FDIS 11133:2013.

Methods: Culture media for pre-enrichment, selective enrichment and isolation were tested according to the methods given by ISO FDIS 11133:2013. Test strains and inocula were prepared from fresh cultures in Tryptic Soy broth and diluted to the desired number of organisms for inoculation: for testing on productivity 10-100 CFU and for selectivity ≥ 10⁴ CFU per tube or plate. Performance evaluation and interpretation of the results followed the specifications given by the Standard.

Results: Culture media for pre-enrichment (Buffered Peptone Water), selective enrichment (Fraser Broth) and solid isolation media (Baird Parker agar, Listeria agar acc. to Agosti and Ottaviani, Plate Count agar) showed on a minimum of 3 production batches the required criteria for productivity, selectivity and specificity (were applicable). Quantitative productivity tests met the required performance criteria PR ≥0,5 for the selective media (Baird-Parker agar: 2 strains, Listeria agar: 2 strains) and PR≥0,7 for non-selective media (Plate Count agar: 4 strains).

Significance: For the tested media the results of this study indicate the applicability of the methods and criteria for the performance testing of culture media as given in the revised International Standard ISO FDIS 11133:2013.