FprEN ISO 6888-2
(Main)Microbiology of the food chain - Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) - Part 2: Method using rabbit plasma fibrinogen agar medium (ISO/FDIS 6888-2:2021)
Microbiology of the food chain - Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) - Part 2: Method using rabbit plasma fibrinogen agar medium (ISO/FDIS 6888-2:2021)
Mikrobiologie der Lebensmittelkette - Horizontales Verfahren für die Zählung von koagulase-positiven Staphylokokken (Staphylococcus aureus und andere Spezies) - Teil 2: Verfahren mit Kaninchenplasma/Fibrinogen-Agar (ISO/FDIS 6888-2:2021)
Dieses Dokument legt ein horizontales Verfahren für die Zählung von koagulase-positiven Staphylokokken in Lebensmitteln und Futtermitteln fest. In diesem Verfahren werden nach aerober Inkubation bei 34 °C bis 38 °C auf einem festen Medium (Kaninchen-Plasma-Fibrinogen-Medium) erhaltene Kolonien gezählt und bestätigt (siehe Literaturhinweis [10]).
Dieses Dokument ist anzuwenden für:
— Erzeugnissen, die für den menschlichen Verzehr vorgesehen sind;
— Erzeugnissen, die als Futtermittel vorgesehen sind;
— Umgebungsproben im Bereich der Herstellung und Handhabung von Lebensmitteln und Futtermitteln;
— Proben aus dem Bereich der Primärproduktion.
Dieses horizontale Verfahren wurde ursprünglich dazu entwickelt, alle Proben, die zu einer Lebensmittelkette zählen, zu überprüfen.
Wegen der Vielzahl der Produkte in der Lebensmittelkette ist es möglich, dass dieses horizontale Verfahren für alle Produkte nicht bis ins Einzelne geeignet ist. Dennoch wird erwartet, dass die erforderlichen Modifikationen derart gering gehalten werden, dass sie nicht zu einer erheblichen Abweichung von diesem horizontalen Verfahren führen.
Entsprechend den zum Zeitpunkt der Veröffentlichung dieses Dokuments verfügbaren Informationen gilt dieses Verfahren nicht als (vollständig) geeignet für die Untersuchung von fermentierten Produkten oder sonstigen Produkten, die auf Staphylococcus spp basierende technologische Flora enthalten (z. B. S. xylosus) (wie z. B. Rohmilchkäse und bestimmte rohe Fleischerzeugnisse), die wahrscheinlich kontaminiert sind durch:
— Staphylokokken, die auf Baird-Parker-Agar atypische Kolonien bilden;
— Begleitflora, die die gesuchten Kolonien überdecken kann.
Trotzdem sind ISO 6888 1 und dieses Dokument gleichwertig.
WARNUNG — Zum Schutz der Gesundheit des Laborpersonals ist es wesentlich, die Prüfungen zur Zählung von Staphylokokken nur in angemessen ausgerüsteten Laboratorien durchzuführen, wobei die Prüfung unter der Leitung eines erfahrenen Mikrobiologen erfolgt, und dass bei der Entsorgung von bebrüteten Materialien mit großer Sorgfalt vorgegangen wird. Anwender dieses Dokuments sollten mit der üblichen Laborpraxis vertraut sein. Dieses Dokument gibt nicht vor, alle unter Umständen mit der Anwendung des Verfahrens verbundenen Sicherheitsaspekte anzusprechen. Es liegt in der Verantwortlichkeit des Anwenders, geeignete Gesundheits- und Sicherheitsmaßnahmen festzulegen.
Microbiologie de la chaîne alimentaire - Méthode horizontale pour le dénombrement des staphylocoques à coagulase positive (Staphylococcus aureus et autres espèces) - Partie 2 : Méthode utilisant le milieu gélosé au plasma de lapin et au fibrinogène (ISO/FDIS 6888-2:2021)
Mikrobiologija v prehranski verigi - Horizontalna metoda za štetje koagulazno pozitivnih stafilokokov (Staphylococcus aureus in drugih vrst) - 2. del: Metoda uporabe agarja z zajčjo plazmo iz fibrinogenov (ISO/FDIS 6888-2:2021)
General Information
RELATIONS
Standards Content (sample)
SLOVENSKI STANDARD
oSIST prEN ISO 6888-2:2020
01-maj-2020
Mikrobiologija v prehranski verigi - Horizontalna metoda za štetje koagulazno
pozitivnih stafilokokov (Staphylococcus aureus in drugih vrst) - 2. del: Tehnika
uporabe agarja z zajčjo plazmo iz fibrinogenov (ISO/DIS 6888-2:2020)
Microbiology of the food chain - Horizontal method for the enumeration of coagulase-
positive staphylococci (Staphylococcus aureus and other species) - Part 2: Technique
using rabbit plasma fibrinogen agar medium (ISO/DIS 6888-2:2020)Mikrobiologie der Lebensmittelkette - Horizontales Verfahren für die Zählung von
koagulase-positiven Staphylokokken (Staphylococcus aureus und andere Spezies) - Teil
2: Verfahren mit Kaninchenplasma/Fibrinogen-Agar (ISO/DIS 6888-2:2020)Microbiologie des aliments - Méthode horizontale pour le dénombrement des
staphylocoques à coagulase positive (Staphylococcus aureus et autres espèces) - Partie
2: Technique utilisant le milieu gélosé au plasma de lapin et au fibrinogène (ISO/DIS
6888-2:2020)Ta slovenski standard je istoveten z: prEN ISO 6888-2
ICS:
07.100.30 Mikrobiologija živil Food microbiology
oSIST prEN ISO 6888-2:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN ISO 6888-2:2020
DRAFT INTERNATIONAL STANDARD
ISO/DIS 6888-2
ISO/TC 34/SC 9 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2020-03-09 2020-06-01
Microbiology of the food chain — Horizontal method
for the enumeration of coagulase-positive staphylococci
(Staphylococcus aureus and other species) —
Part 2:
Technique using rabbit plasma fibrinogen agar medium
Microbiologie des aliments — Méthode horizontale pour le dénombrement des staphylocoques à coagulase
positive (Staphylococcus aureus et autres espèces) —Partie 2: Technique utilisant le milieu gélosé au plasma de lapin et au fibrinogène
ICS: 07.100.30THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 6888-2:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2020
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COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2020 – All rights reserved
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Contents Page
Foreword ........................................................................................................................................................................................................................................iv
Introduction ..................................................................................................................................................................................................................................v
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ...................................................................................................................................................................................... 1
3 Terms and definitions ..................................................................................................................................................................................... 1
4 Principle ........................................................................................................................................................................................................................ 2
4.1 General ........................................................................................................................................................................................................... 2
4.2 Incubation ................................................................................................................................................................................................... 2
4.3 Enumeration ............................................................................................................................................................................................. 2
5 Culture media and reagents ...................................................................................................................................................................... 2
6 Equipment and consumables .................................................................................................................................................................. 3
7 Sampling ........................................................................................................................................................................................................................ 3
8 Preparation of the test sample ............................................................................................................................................................... 4
9 Procedure..................................................................................................................................................................................................................... 4
9.1 Test portion, initial suspension and dilutions .............................................................................................................. 4
9.2 Inoculation and incubation .......................................................................................................................................................... 4
9.3 Counting of colonies ........................................................................................................................................................................... 4
10 Expression of results ........................................................................................................................................................................................ 4
10.1 General case ............................................................................................................................................................................................... 5
10.2 Estimation of low numbers .......................................................................................................................................................... 5
11 Performance characteristics of the method ............................................................................................................................. 6
11.1 Interlaboratory study ........................................................................................................................................................................ 6
11.2 Repeatability limit ................................................................................................................................................................................ 6
11.3 Reproducibility limit .......................................................................................................................................................................... 7
12 Test report ................................................................................................................................................................................................................... 7
13 Quality assurance ................................................................................................................................................................................................ 8
Annex A (normative) Flow diagram of the procedure ........................................................................................................................ 9
Annex B (normative) Culture media and reagents .............................................................................................................................10
Annex C (informative) Results of the interlaboratory study .....................................................................................................13
Bibliography .............................................................................................................................................................................................................................15
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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.The procedures used to develop this document and those intended for its further maintenance are
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www .iso .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 6888-2:1999), which has been technically
revised.The main changes compared to the previous edition are as follows:
— Title relates to “Food chain”;
— Precision on the status of ISO 6888 part 1 and part 2;
— Consistency with ISO 7218 (2007, Amdt 1 2013): one plate per dilution and pour molten agar medium
at 44 °C to 47 °C;— All occurrences when appropriate; “35 °C or 37 °C” to “34 °C to 38 °C”;
— Normative reference ISO 11133;
— All available standards related to sampling techniques;
— Precision data;
— Flow diagram procedure in Annex A;
— Culture media and reagent with performance testing in Annex B;
— Performance testing for RPFA;
— Results of the interlaboratory study;
— Updated bibliography.
A list of all parts in the ISO 6888 series can be found on the ISO website.
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Introduction
1.1 Because of the large variety of food and feed products, this horizontal method may not be
appropriate in every detail for certain products. In this case, different methods, which are specific to
these products, may be used if absolutely necessary for justified technical reasons. Nevertheless, every
attempt should be made to apply this horizontal method as far as possible.When this part of ISO 6888 is next reviewed, account will be taken of all information then available
regarding the extent to which this horizontal method has been followed and the reasons for deviations
from this method in the case of particular products.The harmonization of test methods cannot be immediate and, for certain group of products,
International Standards and/or national standards may already exist that do not comply with this
horizontal method. It is hoped that when such standards are reviewed they will be changed to comply
with this part of ISO 6888 so that eventually the only remaining departures from this horizontal
method will be those necessary for well-established technical reasons.1.2 ISO 6888 describes three horizontal methods (part 1, part 2 and part 3) for the detection
and enumeration of coagulase-positive staphylococci among which enterotoxinogenic strains are
encountered. It is mainly concerned with Staphylococcus aureus, but also with S. intermedius and certain
strains of S. hyicus.“Both parts 1 and 2 of ISO 6888 are given equivalent status. Nevertheless, it is recommended to use the
procedure described in ISO 6888-2 for the foods (such as cheeses made from raw milk and certain raw
meat products) likely to be contaminated by:— staphylococci forming atypical colonies on a Baird-Parker agar medium;
— background flora which can obscure the colonies being sought.
1.3 For the purposes of this part of ISO 6888, the characterisation of staphylococci is based on a
positive coagulase reaction, but it is recognized that some strains of Staphylococcus aureus give weakly
positive coagulase reactions. These latter strains may be confused with other bacteria but they may
be distinguished from such other bacteria by the use of additional tests not included in this part of
ISO 6888, such as the sensitivity to lysostaphin, the production of haemolysin, thermostable nuclease
and acid from mannitol (see ISO 7218 and reference [1]).The main technical changes listed in the Foreword, introduced in this document compared to ISO 6888-2
(1999), are considered as minor (see ISO 17468).They have a minor impact on the performance characteristics of the method.
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oSIST prEN ISO 6888-2:2020
DRAFT INTERNATIONAL STANDARD ISO/DIS 6888-2:2020(E)
Microbiology of the food chain — Horizontal method
for the enumeration of coagulase-positive staphylococci
(Staphylococcus aureus and other species) —
Part 2:
Technique using rabbit plasma fibrinogen agar medium
WARNING — In order to safeguard the health of laboratory personnel, it is essential that tests
for detecting staphylococci are only undertaken in properly equipped laboratories, under the
control of a skilled microbiologist, and that great care is taken in the disposal of all incubated
materials. Persons using this document should be familiar with normal laboratory practice.
This document does not purport to address all of the safety aspects, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices.
1 ScopeThis document specifies a horizontal method for the enumeration of coagulase-positive staphylococci
by counting of colonies obtained on a solid medium (rabbit plasma fibrinogen medium) after aerobic
incubation at 34 °C to 38 °C (see reference [2]).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.
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 — Rules for the preparation of the test sample, of initial
suspension and of decimal dilutions for microbiological examinationISO 7218, Microbiology of food and animal feeding stuffs — General requirements and guidance for
microbiological examinationsISO 11133, Microbiology of food, animal feed and water — Preparation, production, storage and
performance testing of culture mediaISO 17468, Microbiology of the food chain — Technical requirements and guidance on establishment or
revision of a standardized reference method3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp— IEC Electropedia: available at http:// www .electropedia .org/
3.1
coagulase-positive staphylococci
bacteria which form typical colonies in or on a selective culture medium (rabbit plasma fibrinogen
agar medium).Note 1 to entry: : the typical colonies are described in clause 9.3.
3.2
enumeration of the coagulase-positive staphylococci
determination of the number of coagulase-positive staphylococci (3.1) per millilitre or per gram, per
square centimetre or per sampling device..4 Principle
4.1 General
Preparation of poured plate of the rabbit plasma fibrinogen agar medium, with a specified quantity of
the test sample if the product is liquid or with a specified quantity of the initial suspension in the case
of other products.Inoculation, under the same conditions, using decimal dilutions of the test sample or of the initial
suspension, with one plate per dilution.4.2 Incubation
Aerobic incubation of the plates at 34 °C to 38 °C and examination after 24hand if necessary after 48 h.
4.3 EnumerationCalculation of the number of coagulase-positive staphylococci per gram, per millilitre, per square
centimetre or per sampling device of sample from the number of typical colonies obtained on plates at
dilution levels chosen to give a significant result.NOTE See Annex A for flow diagram
5 Culture media and reagents
Follow current laboratory practices in accordance with ISO 7218.
The composition of culture media and reagents and their preparation are specified in Annex B.
For performance testing of culture media, follow the procedures in accordance with ISO 11133 and
Annex B.For the diluent(s), see the relevant part of ISO 6887 series.
Commercially available media, in accordance with this document, can be used. Nevertheless,
considering the known variability of manufactured lots of the supplement, it is recommended that
each batch of bovine fibrinogen/rabbit plasma solution be tested before use, by running positive and
negative controls.2 © ISO 2020 – All rights reserved
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6 Equipment and consumables
Disposable equipment is an acceptable alternative to reusable glassware if it has suitable specifications.
Usual microbiological laboratory equipment (see ISO 7218) and, in particular, the following.
6.1 Apparatus for dry sterilization (oven) and wet sterilization (autoclave)See ISO 7218
6.2 Incubator, capable for maintaining the inoculated media, within the temperature range 34 °C
to 38 °C.NOTE The range 34 °C to 38 °C for incubation of media includes the use of incubators set at 35 °C ± 1 °C or 37
°C ± 1 °C.6.3 Water bath, or similar apparatus, capable of being maintained at 44 °C to 47 °C.
6.4 Petri dishes, with a diameter of approximately 90 mm, sterile, made of glass or plastic.
6.5 Sterile graduated pipettes or automatic pipettes of nominal capacities 1 ml, 2 ml and 10 ml,
graduated in 0,1 ml, 0,1 ml and 0,5 ml divisions, respectively.Graduated pipettes and pipettor tips should be fitted with a non-absorbent cotton wool plug to prevent
contamination when used to manipulate microbial cultures.6.6 pH-meter, it shall be capable of being read to the nearest 0,01 pH unit, enabling measurements
to be made with a tolerance of ±0,1 pH unit. The pH meter shall be equipped with either manual or
automatic temperature compensation.6.7 Refrigerator capable of operating at 5°C±3°C.
7 Sampling
Sampling is not part of the method specified in this document. Follow the specific International
Standard dealing with the product concerned. If there is no specific International Standard dealing
with the sampling of the product concerned, it is recommended that the parties concerned come to an
agreement on this subject.Recommended sampling techniques are given in the following documents:
[3]
— ISO/TS 17728 for food and animal feed ;
[4]
— ISO 707 for milk and milk products ;
[5]
— ISO 6887-3 for fish and fishery products ;
[6]
— ISO 13307 for primary production stage ;
[7]
— ISO 17604 for carcasses ;
[8]
— ISO 18593 for surfaces .
It is important that the laboratory receive a sample which is truly representative and has not been
damaged or changed during transport or storage.© ISO 2020 – All rights reserved 3
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8 Preparation of the test sample
Prepare the test sample from the laboratory sample in accordance with the specific International
Standard dealing with the product concerned: follow the procedures specified in ISO 6887 (all parts).
If there is no specific International Standard available, it is recommended that the parties concerned
come to an agreement on this subject.9 Procedure
9.1 Test portion, initial suspension and dilutions
See the relevant part of ISO 6887 series.
9.2 Inoculation and incubation
9.2.1 Transfer, by means of a sterile pipette (6.5), 1 ml of the test sample if liquid, or 1 ml of the initial
suspension (10 dilution) in the case of other products, to an agar Petri dish (Annex B). For enumeration
techniques in food microbiology, one Petri dish per dilution shall be used with at least two successive
dilutions. Repeat the procedure for the 10- dilution and for further decimal dilutions if necessary. If only
one dilution is plated, two plates have to be used.9.2.2 Into each Petri dish (9.2.1), immediately pour 18 – 20 ml freshly prepared complete medium
(B.2.3) (do not keep this in a liquid form) to obtain a depth of at least 3 mm.Carefully mix the inoculum with the culture medium and leave to solidify by placing the Petri dishes on
a cool horizontal surface.9.2.3 After complete solidification, invert the dishes and place them in the incubator (6.2) set at 34 °C
to 38 °C. Examine plates after 24 h ± 2 h and, if necessary, after 48 h ± 4 h incubation. If no colonies or no
typical colonies are obtained at 24 h ± 2 h, incubate until 48 h ± 4 h.NOTE Colonies with typical appearance after 24 h ± 2 h incubation can lose typical appearance after 48 h
± 4 h incubation, due to enzymatic processes (trypsin) of secondary growth or due to overgrowth by secondary
growth. Counting only at 24 h ± 2 h can lead to too low counts or no counts.9.3 Counting of colonies
After a sufficient incubation period (see 9.2.3), the staphylococci form black or grey or even white,
small colonies surrounded by a halo of precipitation, indicating coagulase activity. Proteus colonies may
appear to look like those of coagulase-positive staphylococci early on in the incubation. However, they
can be distinguished from staphylococci after 24 h and 48 h of incubation, as their colonies become
more or less brownish and start to spread.Count the typical colonies in each dish.
NOTE As the rabbit plasma fibrinogen agar is based on a coagulase reaction, it is not necessary to confirm
this activity.10 Expression of results
For calculation of the results, follow the procedure(s) in accordance with ISO 7218. Calculate and report
the results as the number of coagulase-positive staphylococci in cfu per gram, millilitre, per square
centimetre or per sampling device.In cases where no colonies of the target microorganism have been detected, follow ISO 7218 for the
expression of results for special cases.4 © ISO 2020 – All rights reserved
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10.1 General case
Select those dishes containing at the maximum 300 colonies, with 100 typical colonies per Petri dish.
One dish shall contain at least 10 typical colonies.Calculate the number N of coagulase-positive staphylococci present per millilitre or per gram of product
as a weighted mean from two successive dilutions using the following equation:Vn +01, nd
where
ΣC is the sum of the characteristic staphylococcal colonies on all the dishes selected;
V is the volume of inoculum on each dish, in millilitres;n is the number of dishes selected at the first dilution;
n is the number of dishes selected at the second dilution;
d is the dilution rate corresponding to the first dilution selected (the initial suspension is a
dilution).Round off the calculated results to two significant figures (see ISO 7218).
Take as the result the number of coagulase-positive staphylococci per millilitre (liquid products) or per
gram (other products), expressed as a number between 1,0 and 9,9 inclusive, multiplied by 10 where x
is the appropriate power of 10.EXAMPLE
A count of a product after inoculation with 1 ml of product gave the following results:
— for the first dilution selected (10 ): 66 typical colonies;— for the second dilution selected (10 ): 4 typical colonies.
66+4
N= =6364
11, ×10
The result, after rounding off, is 6,4 x 10 .
10.2 Estimation of low numbers
10.2.1 If the two dishes, corresponding to the test sample (liquid products) or the initial suspension
(other products) each contain less than 15 identified colonies, report the result as follows.
a) For liquid products, estimated number of coagulase-positive staphylococci per millitre (Ne):
N =V×2
where C is the sum of the colonies of coagulase-positive staphylococci counted (9.3) on the two
dishes selected;b) For other products, estimated number of coagulase-positive staphylococci per gram (Ne):
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N =
V××2 d
where
C is the sum of the colonies of coagulase-positive staphylococci counted (9.3) on the two dishes
selected;V is the volume of inoculum on each dish, in millilitres;
d is the dilution rate of the initial suspension.
10.2.2 If the two dishes, corresponding to the test sample (liquid products) or the initial suspension
(other products) do not contain any coagulase-positive staphylococcal colony, report the result as
follows:— less than 1 coagulase-positive staphylococci per millilitre (liquid products);
— less than 1/d coagulase-positive staphylococci per gram (other products), where d is the dilution
rate of the initial suspension.11 Performance characteristics of the method
11.1 Interlaboratory study
Results of the interlaboratory study to determine the precision of the method are summarized in
Annex C. Repeatability and reproducibility limits were determined using five sample types (broiler
caecal material, frozen spinach, minced meat, raw milk, chicken skin) contaminated at various levels.
The values derived from the interlaboratory study may not be applicable to concentration ranges and
sample types other than those given in Annex C.11.2 Repeatability limit
The absolute difference between two single (log -transformed) test results (number of coagulase-
positive staphylococci per gram or per millilitre) or the ratio of the higher to the lower of the two test
results on the normal scale, obtained using the same method on identical test material in the same
laboratory by the same operator using the same equipment within the shortest feasible time interval
will, in no more than 5 % of cases, exceed the repeatability limit r.As a general indication of the repeatability limit r, the following values (med
...
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