SIST-TS CEN ISO/TS 13136:2013

Microbiology of food and animal feed - Real-time polymerase chain reaction (PCR)-based method for the detection of food-borne pathogens - Horizontal method for the detection of Shiga toxin-producing Escherichia coli (STEC) and the determination of O157, O111, O26, O103 and O145 serogroups (ISO/TS 13136:2012)

This Technical Specification 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 (References [2][3]);
b) the genes associated with the serogroups O157, O111, O26, O103, and O145 (References [3][4]). 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 serogroupassociated genes. This Technical Specification 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.

Mikrobiologie von Lebensmitteln und Futtermitteln - Real-time-Polymerase-Kettenreaktion (PCR) zum Nachweis von pathogenen Mikroorganismen in Lebensmitteln - Horizontales Verfahren für den Nachweis von Shiga-Toxin bildenden Escherichia coli (STEC) der Serogruppen O157, O111, O26, O103 und O145 (ISO/TS 13136:2012)

Diese Technische Spezifikation beschreibt ein horizontales Verfahren zum Nachweis:
a)   der wichtigsten Virulenzgene von STEC [2], [3];
b)   der mit den Serogruppen O157, O111, O26, O103 und O145 assoziierten Gene [3], [4].
Im Fall des Nachweises dieser Gene wird versucht, den Stamm zu isolieren, um das gleichzeitige Vorhandensein der Gene in der gleichen, lebenden Bakterienzelle zu bestätigen.
Diese Technische Spezifikation wurde auf der Grundlage der Anwendung von Real-time-PCR als Referenzverfahren zum Nachweis der Virulenzgene und der mit bestimmten Serogruppen-assoziierten Gene entwickelt. Deshalb wird ein Real-time PCR-Protokoll detailliert beschrieben.
Die vorliegende Technische Spezifikation ist anwendbar auf:
-   Erzeugnisse, die für den menschlichen Verzehr und als Futtermittel vorgesehen sind;
-   Umgebungsproben im Bereich der Herstellung und Handhabung von Lebensmitteln;
-   Umgebungsproben im Bereich der Primärproduktion.

Microbiologie des aliments - Méthode basée sur la réaction de polymérisation en chaîne (PCR) en temps réel pour la détection des micro-organismes pathogènes dans les aliments - Méthode horizontale pour la détection des Escherichia coli producteurs de Shigatoxines (STEC) et la détermination des sérogroupes O157, O111, O26, O103 et O145 (ISO/TS 13136:2012)

L'ISO/TS 13136:2012 décrit une méthode horizontale pour la détection: a)des principaux gènes de virulence des STEC; b) des gènes associés aux sérogroupes O157, O111, O26, O103 et O145.
Dans le cas de la détection de ces gènes, une procédure d'isolement de souches est mise en place afin de confirmer la présence simultanée des gènes dans une seule et même cellule bactérienne vivante.
L'ISO/TS 13136:2012 repose sur l'utilisation de la PCR en temps réel comme technologie de référence pour la détection des gènes de virulence et des gènes associés aux sérogroupes. Un protocole de PCR en temps réel est par conséquent décrit en détail.
L'ISO/TS 13136:2012 s'applique: 1) aux produits destinés à être consommés par l'Homme et aux aliments pour animaux; 2) aux échantillons environnementaux dans la zone de production et de manipulation des aliments; 3) aux échantillons environnementaux dans la zone de production primaire.

Mikrobiologija živil in krme - Odkrivanje prisotnosti patogenih mikroorganizmov z metodo na osnovi polimerazne verižne reakcije (PCR) v realnem času - Horizontalna metoda za ugotavljanje prisotnosti Escherichia coli (STEC) ki proizvaja Shiga toksin in določevanje serotipov O157, O111, O26, O103 ter O145 seroskupin (ISO/TS 13136:2012)

Ta tehnična specifikacija opisuje ugotavljanje prisotnosti Escherichia coli, ki proizvajajo toksine šigel (STEC), z odkrivanjem naslednjih genov:
a) glavnih genov virulence STEC, stx in eae (zveze [2][3]);
b) genov, povezanih s serotipi O157, O111, O26, O103 in O145 (zveze [3][4]). V vsakem primeru se poskuša sev izolirati, ko je zaznan eden ali oba gena stx. Izolacija STEC iz vzorcev, pozitivnih na prisotnost genov, ki določajo serotipe na področju uporabe te metode, se lahko olajša z uporabo tehnik obogatitve, specifičnih za serotip (npr. imunomagnetna separacija, IMS). Protokol kot referenčno tehnologijo za odkrivanje virulence in genov, povezanih s serotipom, uporablja polimerazno verižno reakcijo (PCR) v realnem času. Ta tehnična specifikacija se uporablja za:
1) izdelke, namenjene za prehrano ljudi in krmo živali;
2) okoljske vzorce na območju proizvodnje hrane in ravnanja s hrano;
3) okoljske vzorce na območju primarne proizvodnje.

General Information

• Status: Published
• Public Enquiry End Date: 24-May-2012
• Publication Date: 04-Mar-2013
• ICS: 07.100.30 - Food microbiology
• Technical Committee: KŽP - Agricultural food products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 07-Dec-2012
• Due Date: 11-Feb-2013
• Completion Date: 05-Mar-2013
• Ref Project: CEN ISO/TS 13136:2012 - Microbiology of food and animal feed - Real-time polymerase chain reaction (PCR)-based method for the detection of food-borne pathogens - Horizontal method for the detection of Shiga toxin-producing Escherichia coli (STEC) and the determination of O157, O111, O26, O103 and O145 serogroups (ISO/TS 13136:2012)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TS CEN ISO/TS 13136:2013
01-maj-2013
0LNURELRORJLMDåLYLOLQNUPH2GNULYDQMHSULVRWQRVWLSDWRJHQLKPLNURRUJDQL]PRY]
PHWRGRQDRVQRYLSROLPHUD]QHYHULåQHUHDNFLMH3&5YUHDOQHPþDVX
+RUL]RQWDOQDPHWRGD]DXJRWDYOMDQMHSULVRWQRVWL(VFKHULFKLDFROL67(&LQ
GRORþHYDQMHVHURWLSRY2222LQ2,6276
Microbiology of food and animal feed - Real-time polymerase chain reaction (PCR)-
based method for the detection of food-borne pathogens - Horizontal method for the
detection of Shiga toxin-producing Escherichia coli (STEC) and the determination of
O157, O111, O26, O103 and O145 serogroups (ISO/TS 13136:2012)
Mikrobiologie von Lebensmitteln und Futtermitteln - Real-time-Polymerase-
Kettenreaktion (PCR) zum Nachweis von pathogenen Mikroorganismen in Lebensmitteln
- Horizontales Verfahren für den Nachweis von Shiga-Toxin bildenden Escherichia coli
(STEC) der Serogruppen O157, O111, O26, O103 und O145 (ISO/TS 13136:2012)
Microbiologie des aliments - Méthode basée sur la réaction de polymérisation en chaîne
(PCR) en temps réel pour la détection des micro-organismes pathogènes dans les
aliments - Méthode horizontale pour la détection des Escherichia coli producteurs de
Shigatoxines (STEC) et la détermination des sérogroupes O157, O111, O26, O103 et
O145 (ISO/TS 13136:2012)
Ta slovenski standard je istoveten z: CEN ISO/TS 13136:2012
ICS:
07.100.30 Mikrobiologija živil Food microbiology
SIST-TS CEN ISO/TS 13136:2013 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TS CEN ISO/TS 13136:2013

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SIST-TS CEN ISO/TS 13136:2013


TECHNICAL SPECIFICATION
CEN ISO/TS 13136

SPÉCIFICATION TECHNIQUE

TECHNISCHE SPEZIFIKATION
November 2012
ICS 07.100.30
English Version
Microbiology of food and animal feed - Real-time polymerase
chain reaction (PCR)-based method for the detection of food-
borne pathogens - Horizontal method for the detection of Shiga
toxin-producing Escherichia coli (STEC) and the determination
of O157, O111, O26, O103 and O145 serogroups (ISO/TS
13136:2012)
Microbiologie des aliments - Méthode basée sur la réaction Mikrobiologie von Lebensmitteln und Futtermitteln - Real-
de polymérisation en chaîne (PCR) en temps réel pour la time-Polymerase-Kettenreaktion (PCR) zum Nachweis von
détection des micro-organismes pathogènes dans les pathogenen Mikroorganismen in Lebensmitteln -
aliments - Méthode horizontale pour la détection des Horizontales Verfahren für den Nachweis von Shiga-Toxin
Escherichia coli producteurs de Shigatoxines (STEC) et la bildenden Escherichia coli (STEC) der Serogruppen O157,
détermination des sérogroupes O157, O111, O26, O103 et O111, O26, O103 und O145 (ISO/TS 13136:2012)
O145 (ISO/TS 13136:2012)
This Technical Specification (CEN/TS) was approved by CEN on 16 July 2012 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TS 13136:2012: E
worldwide for CEN national Members.

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SIST-TS CEN ISO/TS 13136:2013
CEN ISO/TS 13136:2012 (E)
Contents Page
Foreword .3
2

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SIST-TS CEN ISO/TS 13136:2013
CEN ISO/TS 13136:2012 (E)
Foreword
This document (CEN ISO/TS 13136:2012) has been prepared by Technical Committee CEN/TC 275 “Food
analysis - Horizontal methods” the secretariat of which is held by DIN, in collaboration with Technical
Committee ISO/TC 34 "Food products".
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus,
Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,
Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

3

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SIST-TS CEN ISO/TS 13136:2013

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SIST-TS CEN ISO/TS 13136:2013
TECHNICAL ISO/TS
SPECIFICATION 13136
First edition
2012-11-15
Microbiology of food and animal feed —
Real-time polymerase chain reaction
(PCR)-based method for the detection
of food-borne pathogens — Horizontal
method for the detection of Shiga toxin-
producing Escherichia coli (STEC) and
the determination of O157, O111, O26,
O103 and O145 serogroups
Microbiologie des aliments — Méthode basée sur la réaction de
polymérisation en chaîne (PCR) en temps réel pour la détection
des micro-organismes pathogènes dans les aliments — Méthode
horizontale pour la détection des Escherichia coli producteurs de
Shigatoxines (STEC) et la détermination des sérogroupes O157, O111,
O26, O103 et O145
Reference number
ISO/TS 13136:2012(E)
©
ISO 2012

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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved

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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
4.1 General . 2
4.2 Microbial enrichment . 2
4.3 Nucleic acid extraction . 3
4.4 Target genes . 3
4.5 Detection . 3
4.6 Isolation . 3
5 Diluents, culture media and reagents . 3
5.1 Culture media . 4
5.2 Reagents for nucleic acid extraction . 5
5.3 Reagents for PCR . 5
6 Equipment . 5
7 Sampling . 6
8 Preparation of test sample . 6
9 Procedure . 6
9.1 Test portion and initial suspension . 6
9.2 Enrichment . 7
9.3 Nucleic acid extraction . 7
9.4 PCR amplification (for real-time PCR) . 7
9.5 Strain isolation . 8
10 Expression of results . 8
11 Performance data . 8
Annex A (normative) Flow diagram of the screening procedure .12
Annex B (normative) Flow diagram of the isolation and confirmation procedure .13
Annex C (informative) Identification of Shiga toxin-producing Escherichia coli (STEC) by multiplex
PCR amplification of virulence genes and detection of PCR products by agarose
gel electrophoresis .14
Annex D (informative) Internal amplification control .18
Annex E (informative) Primers and probes for the PCR assays .19
Annex F (normative) Isolation of STEC strains .21
Bibliography .22
© ISO 2012 – All rights reserved iii

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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International
Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a technical
committee may decide to publish other types of document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee
casting a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further
three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed,
it is reviewed again after a further three years, at which time it must either be transformed into an International
Standard or be withdrawn.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TS 13136 was prepared by the European Committee for Standardization (CEN) in collaboration with
Technical Committee ISO/TC 34, Food products, Subcommittee SC 9, Microbiology, in accordance with the
Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
Introduction
Shiga toxin-producing Escherichia coli (STEC) are pathogenic E. coli, which can cause diarrhoea as well as more
severe diseases in humans such as haemorrhagic colitis and haemolytic uremic syndrome (HUS). Although
STEC may belong to a large number of serogroups, those that have been firmly associated with the most severe
forms of the disease, in particular HUS, belong to O157, O26, O111, O103, and O145 (Reference [1]).
The following nomenclature has been adopted in this Technical Specification:
— stx: Shiga toxin genes (synonymous with vtx);
— Stx: Shiga toxin (synonymous with Vtx: Verocytotoxin);
— STEC: Shiga toxin-producing Escherichia coli (synonymous with VTEC: Verocytotoxin-producing
Escherichia coli).
The International Organization for Standardization (ISO) draws attention to the fact that it is claimed that
compliance with this document may involve the use of patents.
ISO takes no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO that he/she is willing to negotiate licences either free of charge
or under reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this
respect, the statement of the holder of this patent right is registered with ISO. Information can be obtained from:
Agence Nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail/
French Agency for Food, Environment and Occupational Health and Safety (ANSES)
10 rue Pierre Curie
F-94700 MAISONS-ALFORT, Cedex
France
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights
other than those identified above. ISO shall not be held responsible for identifying any or all such patent rights.
ISO (www.iso.org/patents) maintains an on-line database of patents relevant to their documents. Users are
encouraged to consult the databases for the most up to date information concerning patents.
© ISO 2012 – All rights reserved v

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SIST-TS CEN ISO/TS 13136:2013
TECHNICAL SPECIFICATION ISO/TS 13136:2012(E)
Microbiology of food and animal feed — Real-time polymerase
chain reaction (PCR)-based method for the detection of food-
borne pathogens — Horizontal method for the detection
of Shiga toxin-producing Escherichia coli (STEC) and the
determination of O157, O111, O26, O103 and O145 serogroups
IMPORTANT — It is necessary to consider any STEC as pathogenic to humans and potentially to cause
severe disease depending on both the risk profile of the food commodity (ready-to-eat foods vs. foods
intended to be consumed after technological treatment such as pasteurization, cooking etc. used to
reduce any bacteria present in the food) and the health status of the subject ingesting the food.
Moreover, given the high genomic plasticity of this bacterial species, it is possible that novel
arrangements of virulence features can give rise to novel sero-pathogroups such as the Shiga toxin-
producing enteroaggregative E. coli O104 that caused the HUS outbreaks in Germany and France in
2011-05/06. Novel atypical E. coli sero-pathogroups can arise from the acquisition of an stx-converting
bacteriophage by an E. coli strain belonging to pathogroups different from STEC.
Such atypical strains fall in the scope of this method and can be efficiently detected as they are positive for the
presence of the stx genes.
1 Scope
This Technical Specification 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 (References [2][3]);
b) the genes associated with the serogroups O157, O111, O26, O103, and O145 (References [3][4]).
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.
This Technical Specification 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.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 7218, Microbiology of food and animal feeding stuffs — General requirements and guidance for
microbiological examinations
© ISO 2012 – All rights reserved 1

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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
ISO 20838, Microbiology of food and animal feeding stuffs — Polymerase chain reaction (PCR) for the detection
of food-borne pathogens — Requirements for amplification and detection for qualitative methods
ISO 22174, Microbiology of food and animal feeding stuffs — Polymerase chain reaction (PCR) for the detection
of food-borne pathogens — General requirements and definitions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
Definitions 3.1 to 3.3 have been compiled from the epidemiological data on disease caused by STEC managed
by organizations such as the US Centers for Disease Control and, in the EU, by the European Centre for
Disease Prevention and Control and the European Food Safety Authority.
3.1
Shiga toxin-producing Escherichia coli
STEC
E. coli strains possessing the Stx-coding genes
3.2
Shiga toxin-producing Escherichia coli causing the attaching and effacing lesion
STEC causing the attaching and effacing lesion
E. coli strains possessing the Stx-coding genes and the intimin-coding gene eae
NOTE This combination of virulence genes is often associated with the most severe forms of STEC-induced disease.
3.3
Shiga toxin-producing Escherichia coli belonging to highly pathogenic serogroups
STEC belonging to highly pathogenic serogroups
E. coli strains possessing the Stx-coding genes, the intimin-coding gene eae and belonging to one of the
serogroups O157, O111, O26, O103, and O145
4 Principle
4.1 General
The method specified comprises the following sequential steps:
a) microbial enrichment;
b) nucleic acid extraction;
c) detection of virulence genes;
d) detection of serogroup-associated genes;
e) isolation from positive samples.
Figure A.1 is a flow diagram of the screening procedure.
4.2 Microbial enrichment
The number of STEC cells to be detected is increased by incubating the test portion in a non-selective liquid
nutrient medium chosen from:
a) modified tryptone-soy broth (tryptone soy broth supplemented with 1,5 g/l bile salts No.3, mTSB)
supplemented with 16 mg/l of novobiocin (mTSB+N);
b) buffered peptone water (BPW);
2 © ISO 2012 – All rights reserved

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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
c) modified tryptone-soy broth (tryptone-soy broth supplemented with 1,5 g/l bile salts No.3, mTSB)
supplemented with 12 mg/l of acriflavin (mTSB+A) for analysis of milk and dairy products.
The mTSB shall be used when analysing matrices suspected to contain high levels of contaminating microflora.
Novobiocin and acriflavin inhibit the growth of Gram-positive bacteria and promote the growth of Gram-negative
cells, including STEC. The BPW shall be used to analyse samples which are assumed to contain stressed
target bacteria (such as frozen products), to resuscitate stressed STEC cells, and expected lower levels of
contaminating microflora than in fresh samples.
NOTE The addition of novobiocin is controversial and has been investigated by several authors. It has been observed
that the minimum inhibitory concentration of the antibiotic for non-O157 STEC is lower than for O157 strains (Reference
[19]
[5]). The addition of novobiocin in the enrichment mTSB at the usual concentration of 20 mg/l, as specified in ISO 16654,
seems to inhibit the growth of about one-third of non-O157 strains (Reference [6]) increasing the risk of false-negative results.
4.3 Nucleic acid extraction
The nucleic acid is extracted according to the requirements of the adopted detection system.
4.4 Target genes
The purified nucleic acid is used for the detection of the following target genes:
— the main virulence genes for STEC: stx genes, encoding the Shiga toxins and the eae gene, encoding a
90 kDa protein, the intimin, involved in the attaching and effacing mechanism of adhesion, a typical feature
of the STEC strains causing severe disease. The stx genes encode a family of toxins including two main
types: stx1 and stx2. The latter comprises seven recognized variants (from stx2a to stx2g) (Reference
[22]). Only the variants stx2a, stx2b, and stx2c have been found to be produced by the STEC strains
included in Clause 1, and therefore constitute the target Stx-coding genes of this Technical Specification.
The GenBank accession numbers corresponding to the stx2 variants-coding genes are:
— stx2a: X07865
— stx2b: L11078
— stx2c: M59432
— the intimin-coding eae gene
— the rfbE(O157), wbdl(O111), wzx(O26), ihp1(O145) and wzx(O103) genes, to identify the corresponding
serogroups.
4.5 Detection
The detection of the target genes is performed according to the adopted detection system.
4.6 Isolation
If the presence of a STEC is suspected, the isolation is attempted. If one of the serogroups specified in the
scope of this Technical Specification is detected, a serogroup-specific enrichment (e.g. IMS) can be performed
followed by plating on to tryptone–bile–glucuronic agar (TBX) or a specific selective medium if available (see
Annex F, Notes 2 and 3) in order to facilitate the isolation of the STEC from the background flora.
5 Diluents, culture media and reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and sterile
distilled or demineralized water or water of equivalent purity.
© ISO 2012 – All rights reserved 3

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ISO/TS 13136:2012(E)
5.1 Culture media
5.1.1 Modified tryptone- soy broth (mTSB)
5.1.1.1 Basic medium
Composition and pH
Enzymatic digest of casein 17 g
Enzymatic digest of soy 3 g
d(+)-Glucose 2,5 g
Sodium chloride 5 g
Dipotassium hydrogenphosphate (K HPO ) 4 g
2 4
Bile salts No. 3 1,5 g
Water to 1 000 ml
pH 7,4 ± 0,2
Preparation
Dissolve the components or the dehydrated medium in water. Adjust pH with a pH-meter to pH 7,4 ± 0,2 at
25 °C and sterilize by autoclaving at 121 °C for 15 min.
5.1.1.2 Novobiocin solution
Composition
Novobiocin 0,16 g
Water 10 ml
Preparation
Dissolve the novobiocin in the water and sterilize by membrane filtration using 0,22 µm or 0,45 µm filters.
Prepare on the day of use.
5.1.1.3 Acriflavin solution
Composition
Acriflavin 0,12 g
Water 10 ml
Preparation
Dissolve the acriflavin in the water and sterilize by membrane filtration using 0,22 µm or 0,45 µm filters.
Prepare on the day of use.
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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
5.1.1.4 Preparation of the complete medium
Immediately before use, add 1 ml of novobiocin (5.1.1.2) or acriflavin solution (5.1.1.3) to 1 000 ml of cooled
mTSB (5.1.1.1).
The final concentration of novobiocin shall be 16 mg/l of mTSB.
The final concentration of acriflavin shall be 12 mg/l of mTSB.
5.1.2 Buffered peptone water (BPW)
Composition and pH
Peptone 10 g
Sodium chloride 5,0 g
Disodium phosphate (Na HPO ) 3,5 g
2 4
Potassium dihydrogenphosphate (KH PO ) 1,5 g
2 4
Water to 1 000 ml
pH 7,0 ± 0,2
Preparation
Dissolve the components or the dehydrated powder in the water. Adjust pH with a pH-meter to pH 7,0 ± 0,2 at
25 °C and sterilize by autoclaving at 121 °C for 15 min.
5.2 Reagents for nucleic acid extraction
The reagents to be used for nucleic acid extraction are not listed, being dependent on the method adopted (9.3).
5.3 Reagents for PCR
See ISO 20838.
5.3.1 Oligonucleotides (primers) and detection probes
Primers and probes for specific detection of the target gene sequences by standard and real-time PCR are
listed in Annexes C and E.
6 Equipment
Usual microbiological laboratory equipment (see ISO 7218) and, in particular, the following.
6.1 Water bath or heating block capable of being maintained at temperatures up to 100 °C.
6.2 Incubator according to ISO 7218, capable of being maintained at 37 °C± 1 °C.
6.3 Nucleic acid extraction apparatus.
Appropriate equipment according to the method adopted (if needed).
[16]
6.4 Pipettes of capacities between 1 µl and 100 µl, ISO 7550.
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SIST-TS CEN ISO/TS 13136:2013
ISO/TS 13136:2012(E)
6.5 Thin walled real-time PCR microtubes (0,2 ml/0,5 ml reaction tubes), multi-well PCR microplates or
other suitable light transparent disposable plasticware.
6.6 Thermal cycler. Several brands of apparatus are available and can be chosen according to the
laboratory policies.
6.7 PCR product detection apparatus.
Light emission following 5’ nuclease PCR assay is detected by the real-time PCR apparatus.
6.8 Peristaltic blender with sterile bags, pos
...