SIST EN ISO 7932:2005

Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of presumptive Bacillus cereus - Colony-count technique at 30 °C (ISO 7932:2004)

This International Standard specifies a horizontal method for the enumeration of viable presumptive Bacillus
cereus by means of the colony-count technique at 30 °C. It is applicable to
 products intended for human consumption and the feeding of animals, and
 environmental samples in the area of food production and food handling.
NOTE In order to have a practicable test method, the confirmatory stage has been restricted to the typical aspect on
MYP agar and the haemolysis test. Thus the term “presumptive” has been introduced in order to acknowledge the fact that
the confirmatory stage does not enable the distinction of B. cereus from other closely related but less commonly
encountered Bacillus species, such as B. anthracis, B. thuringiensis, B. weihenstephanensis, B. mycoides. An additional
motility test may help to differentiate B. cereus from B. anthracis in cases where the presence of the latter is suspected.

Mikrobiologie von Lebensmitteln und Futtermitteln - Horizontales Verfahren zur Zählung von präsumtivem Bacillus cereus - Koloniezählverfahren bei 30° C (ISO 7932:2004)

Diese Internationale Norm legt ein horizontales Verfahren zur Zählung vermehrungsfähiger Stämme von präsumtivem Bacillus cereus mittels des Koloniezählverfahrens bei 30 °C fest. Es gilt für
3   Erzeugnisse, die für den menschlichen Verzehr oder als Futtermittel bestimmt sind, und
3   Umgebungsproben im Bereich der Herstellung und Behandlung von Lebensmitteln.
ANMERKUNG   Im Sinne der Praktikabilität des Untersuchungsverfahrens beschränkt sich die Bestätigungsunter-suchung auf den Nachweis typischer Aspekte auf MYP-Agar und auf den Hämolysetest. Resultierend daraus wird der Begriff "präsumtiv" verwendet, wodurch anerkannt wird, dass die Bestätigungsuntersuchungen nicht geeignet sind, zwischen B. cereus and den anderen nahe verwandten, aber weniger häufig nachzuweisenden Bazillenarten, wie B. anthracis, B. thuringiensis, B. weihenstephanensis und B. mycoides zu unterscheiden. Wenn die Anwesenheit von B. anthracis vermutet wird, kann eine zusätzliche Mobilitätsprüfung dazu dienen, B. cereus von B. anthracis zu unterscheiden.

Microbiologie des aliments - Méthode horizontale pour le dénombrement de Bacillus cereus présomptifs - Technique par comptage des colonies a 30 °C (ISO 7932:2004)

L'ISO 7932:2004 spécifie une méthode horizontale pour le dénombrement de Bacillus cereus présomptifs revivifiables par comptage des colonies à 30 °C. Elle est applicable aux produits pour l'alimentation humaine et animale; et aux échantillons d'environnement pour la production et la distribution des aliments.
Dans le but de mettre en oeuvre une méthode pratique, l'étape de confirmation consiste uniquement à la caractérisation des colonies sur le milieu MYP et au test de l'hémolyse. Le terme «présomptif» a donc été introduit de façon à souligner le fait que l'étape de confirmation ne permet pas de faire la différence entre B. cereus et d'autres espèces proches mais néanmoins moins rencontrées, comme B. anthracis, B. thuringiensis, B. weihenstephanensis, B. mycoides. Un test de mobilité effectué en plus peut toutefois aider à la différentiation entre B. cereus et B. anthracis, dans les cas où la présence de ce dernier est suspectée.

Mikrobiologija živil in krme - Splošno navodilo za štetje domnevno prisotnih Bacillus cereus - Štetje kolonij pri 30 °C (ISO 7932:2004)

General Information

• Status: Published
• Publication Date: 31-May-2005
• ICS: 07.100.30 - Food microbiology
• Technical Committee: KŽP - Agricultural food products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jun-2005
• Due Date: 01-Jun-2005
• Completion Date: 01-Jun-2005
• Ref Project: EN ISO 7932:2004 - Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of presumptive Bacillus cereus - Colony-count technique at 30 °C (ISO 7932:2004)

Relations

• Replaces: SIST EN ISO 7932:1998 - Microbiology - General guidance for the enumeration of Bacillus cereus - Colony-count technique at 30 °C (ISO 7932:1993, including Technical Corrigendum 1:1997)
• Effective Date: 01-Jun-2005
• Amended By: SIST EN ISO 7932:2005/A1:2020 - Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of presumptive Bacillus cereus - Colony-count technique at 30 degrees C - Amendment 1: Inclusion of optional tests (ISO 7932:2004/Amd 1:2020)
• Effective Date: 01-Jun-2020

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 7932:2005
01-junij-2005
1DGRPHãþD
SIST EN ISO 7932:1998
Mikrobiologija živil in krme - Splošno navodilo za štetje domnevno prisotnih
Bacillus cereus - Štetje kolonij pri 30 °C (ISO 7932:2004)
Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of
presumptive Bacillus cereus - Colony-count technique at 30 °C (ISO 7932:2004)
Mikrobiologie von Lebensmitteln und Futtermitteln - Horizontales Verfahren zur Zählung
von präsumtivem Bacillus cereus - Koloniezählverfahren bei 30° C (ISO 7932:2004)
Microbiologie des aliments - Méthode horizontale pour le dénombrement de Bacillus
cereus présomptifs - Technique par comptage des colonies a 30 °C (ISO 7932:2004)
Ta slovenski standard je istoveten z: EN ISO 7932:2004
ICS:
07.100.30 Mikrobiologija živil Food microbiology
SIST EN ISO 7932:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 7932:2005

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SIST EN ISO 7932:2005



EUROPEAN STANDARD
EN ISO 7932

NORME EUROPÉENNE

EUROPÄISCHE NORM
December 2004
ICS 07.100.01 Supersedes EN ISO 7932:1997
English version
Microbiology of food and animal feeding stuffs - Horizontal
method for the enumeration of presumptive Bacillus cereus -
Colony-count technique at 30 °C (ISO 7932:2004)
Microbiologie des aliments - Méthode horizontale pour le
dénombrement de Bacillus cereus présomptifs - Technique
par comptage des colonies à 30 °C (ISO 7932:2004)
This European Standard was approved by CEN on 17 June 2004.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.

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




EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7932:2004: E
worldwide for CEN national Members.

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SIST EN ISO 7932:2005
EN ISO 7932:2004 (E)


Foreword

This document (EN ISO 7932:2004) has been prepared by Technical Committee ISO/TC 34
"Agricultural food products" in collaboration with Technical Committee CEN/TC 275 "Food
analysis - Horizontal methods", the secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by June 2005, and conflicting national standards
shall be withdrawn at the latest by June 2005.

This document supersedes EN ISO 7932 :1997.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Cyprus,
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice

The text of ISO 7932:2004 has been approved by CEN as EN ISO 7932:2004 without any
modifications.
2

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SIST EN ISO 7932:2005


INTERNATIONAL ISO
STANDARD 7932
Third edition
2004-06-15


Microbiology of food and animal feeding
stuffs — Horizontal method for the
enumeration of presumptive Bacillus
cereus — Colony-count technique at
30 °C
Microbiologie des aliments — Méthode horizontale pour le
dénombrement de Bacillus cereus présomptifs — Technique par
comptage des colonies à 30 °C




Reference number
ISO 7932:2004(E)
©
ISO 2004

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SIST EN ISO 7932:2005
ISO 7932:2004(E)
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ii © ISO 2004 – All rights reserved

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SIST EN ISO 7932:2005
ISO 7932:2004(E)
Contents Page
Foreword. iv
0 Introduction . v
1 Scope. 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle . 1
5 Dilution fluid, culture media and reagents . 2
6 Apparatus and glassware. 4
7 Sampling . 5
8 Preparation of test sample. 5
9 Procedure. 5
9.1 Test portion, initial suspension and dilutions . 5
9.2 Inoculation and incubation . 5
9.3 Counting of the colonies. 5
9.4 Confirmation. 6
10 Expression of results. 6
10.1 Count of presumptive B. cereus colonies. 6
10.2 No colonies. 7
10.3 Precision . 7
11 Test report. 8
Annex A (normative) Confidence limits for the estimation of small numbers of colonies. 9
Annex B (informative) Results of interlaboratory test . 10
Bibliography . 13

© ISO 2004 – All rights reserved iii

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SIST EN ISO 7932:2005
ISO 7932:2004(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.
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 7932 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 9,
Microbiology.
This third edition cancels and replaces the second edition (ISO 7932:1993) and Technical Corrigendum 1
(ISO 7932:1993/Cor.1:1997).
In this edition the previous confirmation tests [mannitol/egg yolk/polymyxin (MYP) agar medium, glucose
fermentation, Voges-Proskauer reaction and nitrate reduction] are replaced by the following:
 haemolysis reaction;
 MYP agar medium.
This edition introduces precision data obtained during an interlaboratory trial based on ISO 7932:1993 and
using the following confirmation tests: MYP agar medium, glucose agar medium, VP medium and nitrate
medium.

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SIST EN ISO 7932:2005
ISO 7932:2004(E)
0 Introduction
0.1 This International Standard is intended to provide general guidance for the microbiological examination
of food products not dealt with by existing International Standards and to be taken into account by
organizations preparing microbiological test methods for application to foods or to animal feeding stuffs.
Because of the large variety of products within this field of application, these guidelines may not be
appropriate in every detail for certain products and for some other products it may be necessary to use
different methods. Nevertheless, it is hoped that in all cases every attempt will be made to apply the
guidelines provided as far as possible and that deviations from them will only be made if absolutely necessary
for technical reasons.
When this International Standard is next reviewed, account will be taken of all information then available
regarding the extent to which the guidelines have been followed and the reasons for deviation from them in
the case of particular products.
The harmonization of test methods cannot be immediate and, for certain groups of products, International
Standards and/or national standards may already exist that do not comply with the guidelines. In cases where
International Standards already exist for the product to be tested, they should be followed, but it is hoped that
when such standards are reviewed they will be changed to comply with this International Standard so that
eventually the only remaining departures from these guidelines will be those necessary for well-established
technical reasons.
0.2 It appears that the spores of many, if not most, strains of B. cereus germinate readily on the surface of
culture media used for enumeration. In most cases there does not seem to be a need for heat shock treatment
to provoke germination. Sometimes a heat shock procedure is desirable, for example for spore counts or to
inhibit growth of vegetative bacterial cells. In such cases, treatment for 10 min at 80 °C is recommended.

© ISO 2004 – All rights reserved v

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SIST EN ISO 7932:2005

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SIST EN ISO 7932:2005
INTERNATIONAL STANDARD ISO 7932:2004(E)

Microbiology of food and animal feeding stuffs — Horizontal
method for the enumeration of presumptive Bacillus cereus —
Colony-count technique at 30 °C
1 Scope
This International Standard specifies a horizontal method for the enumeration of viable presumptive Bacillus
cereus by means of the colony-count technique at 30 °C. It is applicable to
 products intended for human consumption and the feeding of animals, and
 environmental samples in the area of food production and food handling.
NOTE In order to have a practicable test method, the confirmatory stage has been restricted to the typical aspect on
MYP agar and the haemolysis test. Thus the term “presumptive” has been introduced in order to acknowledge the fact that
the confirmatory stage does not enable the distinction of B. cereus from other closely related but less commonly
encountered Bacillus species, such as B. anthracis, B. thuringiensis, B. weihenstephanensis, B. mycoides. An additional
motility test may help to differentiate B. cereus from B. anthracis in cases where the presence of the latter is suspected.
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 6887-1:1999, Microbiology of food and animal feeding stuffs — Preparation of test samples, initial
suspension and decimal dilutions for microbiological examination — Part 1: General rules for the preparation
of the initial suspension and decimal dilutions
ISO 7218:1996, Microbiology of food and animal feeding stuffs — General rules for microbiological examinations,
and Amd.1:2001
ISO/TS 11133-2:2003, Microbiology of food and animal feeding stuffs — Guidelines on preparation and
production of culture media — Part 2: Practical guidelines on performance testing of culture media
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
presumptive Bacillus cereus
microorganism that forms typical colonies on the surface of a selective culture medium and which gives a
positive confirmation reaction under the conditions specified in this International Standard
NOTE See Note in Clause 1.
4 Principle
4.1 A specified quantity of the test sample if the initial product is liquid, or a specified quantity of an initial
suspension in the case of other products, is surface plated on a solid selective culture medium contained in
Petri dishes.
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SIST EN ISO 7932:2005
ISO 7932:2004(E)
Other plates are prepared under the same conditions, using decimal dilutions of the test sample or of the initial
suspension.
4.2 The plates are incubated under aerobic conditions at 30 °C for 18 h to 48 h.
4.3 The number of B. cereus per gram or per millilitre of sample is calculated from the number of confirmed
colonies obtained on plates at dilution levels chosen so as to give a significant result, and confirmed according
to the test specified.
5 Dilution fluid, culture media and reagents
For current laboratory practice, see ISO 7218.
NOTE Commercially prepared ready-to-use reagents may be used.
5.1 Dilution fluid
See ISO 6887-1 and any specific standard dealing with the product to be examined.
5.2 Agar medium (see [1])
5.2.1 Base medium
5.2.1.1 Composition
Beef extract 1,0 g
Enzymatic digest of casein 10,0 g
D-Mannitol 10,0 g
Sodium chloride (NaCl) 10,0 g
Phenol red 0,025 g
a
Agar 12 g to 18 g
Water 900 ml
a
Depending on the gel strength of the agar.

5.2.1.2 Preparation
Dissolve the components or the dehydrated complete medium in the water, by heating if necessary.
Adjust the pH, if necessary, so that the pH of the complete medium (5.2.4), after sterilization, is 7,2 ± 0,2 at
25 °C.
Dispense the medium in quantities of 90 ml into flasks of appropriate capacity.
Sterilize for 15 min in an autoclave (6.1) set at 121 °C.
5.2.2 Polymyxin B solution
5.2.2.1 Composition
6
Polymyxin B sulfate 10 IU
Water 100 ml

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SIST EN ISO 7932:2005
ISO 7932:2004(E)
5.2.2.2 Preparation
Dissolve the polymyxin B sulfate in the water. Sterilize by filtration.
5.2.3 Egg yolk emulsion
Use fresh hens' eggs with their shells intact. Wash the eggs in liquid detergent using a brush. Rinse under
running water, dip in 95 % (by volume) ethanol for 30 s and dry. Using aseptic procedures, break each egg
and separate the yolk from the white by repeatedly transferring the yolk from one half of the egg shell to the
other. Put the yolks into a sterile measuring cylinder and add four parts by volume of sterile water. Transfer
aseptically into a sterile flask and mix vigorously.
Heat the mixture for 2 h in a water bath (6.4) set at 44 °C to 47 °C. Then leave for 18 h to 24 h at 5 °C ± 3 °C
to allow a precipitate to form.
Collect the supernatant emulsion aseptically.
The emulsion may be stored at 5 °C ± 3 °C for not longer than 72 h.
5.2.4 Complete medium (MYP agar)
5.2.4.1 Composition
Base medium (5.2.1) 90 ml
Polymyxin B solution (5.2.2) 1,0 ml
Egg yolk emul
...