Standards Development

Scope

This document is applicable to pure cultures of STEC. The present standard describes the characterization of STEC strains, isolated from any source. In particular, the characterization of STEC strains described here regard:

- subtyping of the Stx-coding genes; - determination of the presence of eae gene;

- determination of the presence of aggR gene;

- identification of the presence of genes associated to the following serogroups: O157, O26, O111, O103, O145, O121 and O45.

The full characterization of the isolated STEC strains is achieved by performing all the modules described here. The characterization scheme is not sequential, and the different modules can be implemented separately based on specific needs (e.g. Regulatory needs, Competent Authority’s requests, clients’ request). Alternative methods may be used, including Whole Genome Sequencing (WGS), provided these are verified according to the reference standard ISO 16140-2.

Purpose

The proposal of revising the ISO TS 13136 was announced in 2015, at the CEN general meeting. The request was based on the experience gained following the three years use of this technical specification, concerning several aspects, including the enrichment conditions, the better description of the isolation attempt and the reporting of the results. It concerns a major revision of the ISO TS 13136, which was carried out by a group of experts consisting in the former CEN TC275 WG6 TAG18 and the existing CEN TC463 WG2, being Part 2 dedicated to the characterization of isolated STEC, in line with the most recent pathogenicity assessment issued by EFSA in 2020 (EFSA Journal 2020;18(1):5967) and assisting the international regulations on STEC.