ISO 13722:2017

INTERNATIONAL ISO
STANDARD 13722
Second edition
2017-07
Microbiology of the food chain —
Enumeration of Brochothrix spp. —
Colony-count technique
Microbiologie de la chaine alimentaire — Dénombrement de
Brochothrix spp. — Technique par comptage des colonies
obtenues
Reference number
ISO 13722:2017(E)
©
ISO 2017

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ISO 13722:2017(E)

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© ISO 2017, Published in Switzerland
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ISO 13722:2017(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Culture media and reagents . 2
6 Equipment and consumables . 2
7 Sampling . 2
8 Preparation of test sample . 3
9 Procedure. 3
9.1 Test portion, initial suspension and dilutions . 3
9.2 Inoculation and incubation . 3
9.3 Counting of the colonies . 3
9.4 Confirmation . 3
9.4.1 General. 3
9.4.2 Oxidase test . 4
9.4.3 Catalase test . 4
10 Expression of results . 4
11 Performance characteristics of the method . 4
11.1 Interlaboratory study . 4
11.2 Repeatability and reproducibility limit . 4
12 Test report . 4
Annex A (normative) Culture media and reagents . 6
Bibliography . 9
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ISO 13722:2017(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
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electrotechnical standardization.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 9,
Microbiology.
This second edition cancels and replaces the first edition (ISO 13722:1996), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— the method specified in this document has been aligned with the NMKL (Nordic Committee on Food
Analysis) method described in Reference [8];
— the title has been changed from ‘Meat and meat products’ into ‘Microbiology of the food chain’ and
from ‘Enumeration of Brochothrix thermosphacta’ into ‘Enumeration of Brochothrix spp.’, and the
scope has been changed accordingly;
— actidione (cycloheximide) has been omitted from the enumeration medium because of its toxicity;
— the catalase test has been added as confirmation test;
[8]
— validation data from an NMKL study have been included (Clause 11).
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INTERNATIONAL STANDARD ISO 13722:2017(E)
Microbiology of the food chain — Enumeration of
Brochothrix spp. — Colony-count technique
1 Scope
This document specifies a method for the enumeration of viable Brochothrix spp. by means of a colony-
count technique.
This document is especially applicable to meat and meat products, but is also suitable for the
examination of the following:
— other 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.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 6887 (all parts), Microbiology of the food chain — Preparation of test samples, initial suspension and
decimal dilutions for microbiological examination
ISO 7218, Microbiology of food and animal feeding stuffs — General requirements and guidance for
microbiological examinations
ISO 11133, Microbiology of food, animal feed and water — Preparation, production, storage and
performance testing of culture media
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www.e lectropedia. org/
— ISO Online browsing platform: available at http:// www. iso. org/o bp
3.1
Brochothrix spp.
Gram-positive bacteria which form characteristic oxidase-negative and catalase-positive colonies on a
solid selective medium [streptomycin sulfate/thallium acetate agar (STAA)] under the test conditions
specified in this document
Note 1 to entry: To date only two species of Brochothrix have been described, Br. thermosphacta and Br. campestris.
Br. thermosphacta has often been reported in meat and meat products, but Br. campestris has so far only been
[9,10]
identified in samples from soil and grass. The method described in this document cannot differentiate
between these two species.
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ISO 13722:2017(E)

4 Principle
4.1 Surface plating, on a solid selective culture medium contained in Petri dishes, of a specified quantity
of the test sample if the initial product is liquid, or of a specified quantity of the initial suspension in the
case of other products. Preparation of other plates, under the same conditions, using decimal dilutions of
the test sample or of the initial suspension.
4.2 Incubation of the plates between 22 °C and 25 °C for 48 h.
4.3 Subjection of the colonies to confirmation tests.
4.4 From the number of colonies confirmed, calculation of the number of Brochothrix spp. per millilitre
or per gram of sample from colonies obtained on plates at dilution levels chosen so as to give the most
reliable result.
5 Culture media and reagents
Follow current laboratory practices as specified in ISO 7218.
Carry out the performance testing of culture media as specified in ISO 11133.
The composition of culture media and reagents and their preparation are specified in Annex A.
6 Equipment and consumables
Disposable equipment is an acceptable alternative to reusable glassware if it has suitable specifications.
Usual microbiological laboratory equipment, as specified in ISO 7218, and, in particular, the following.
6.1 Apparatus for dry heat sterilization (oven) or wet heat sterilization (autoclave).
6.2 Incubator or drying cabinet, capable of operating between 25 °C and 50 °C.
6.3 Incubator, capable of operating between 22 °C and 25 °C.
6.4 Petri dishes, made of glass or plastic, of diameter 90 mm to 100 mm.
6.5 pH-meter, accurate to within ±0,1 pH unit
...