CEN/TC 463/WG 2 - Shiga toxin producing Escherichia coli (STEC)

ISO/TR 13136:2012 describes the identification of Shiga toxin-producing Escherichia coli (STEC) by means of the detection of the following genes: a) the major virulence genes of STEC, stx and eae; b) the genes associated with the serogroups O157, O111, O26, O103, and O145.
In any case, when one or both of the stx genes is/are detected, the isolation of the strain is attempted.
The isolation of STEC from samples positive for the presence of the genes specifying the serogroups in the scope of this method can be facilitated by using serogroup-specific enrichment techniques (e.g. immunomagnetic separation, IMS).
The protocol uses real-time PCR as the reference technology for detection of the virulence and serogroup-associated genes.
ISO/TR 13136:2012 is applicable to: 1) products intended for human consumption and the feeding of animals; 2) environmental samples in the area of food production and food handling; 3) environmental samples in the area of primary production.

This standard describes the detection and isolation of Shiga toxin-producing Escherichia coli (STEC). The procedure includes the detection by Real Time PCR of the major virulence genes of STEC, stx1 and stx2 (Reference [2]) in enrichment cultures. Isolation of STEC from the enrichment culture is attempted if one or both stx genes are detected in the screening.
This document is applicable to
-   products intended for human consumption,
-   products intended for animal feeding,
-   environmental samples in the area of food and feed production, handling, and
-   samples from the primary production stage.

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.