SIST EN ISO 6785:2007

SLOVENSKI STANDARD
SIST EN ISO 6785:2007
01-oktober-2007
0OHNRLQPOHþQLSURL]YRGL8JRWDYOMDQMHSULVRWQRVWLYUVW6DOPRQHOOD,62

Milk and milk products - Detection of Salmonella spp. (ISO 6785:2001)
Milch und Milcherzeugnisse - Nachweis von Salmonella spp. (ISO 6785:2001)
Lait et produits laitiers - Recherche de Salmonella spp. (ISO 6785:2001)
Ta slovenski standard je istoveten z: EN ISO 6785:2007
ICS:
07.100.30 Mikrobiologija živil Food microbiology
67.100.01 0OHNRLQPOHþQLSURL]YRGLQD Milk and milk products in
VSORãQR general
SIST EN ISO 6785:2007 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN ISO 6785
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2007
ICS 07.100.30

English Version
Milk and milk products - Detection of Salmonella spp. (ISO
6785:2001)
Lait et produits laitiers - Recherche de Salmonella spp. Milch und Milcherzeugnisse - Nachweis von Salmonella
(ISO 6785:2001) spp. (ISO 6785:2001)
This European Standard was approved by CEN on 19 May 2007.
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 CEN Management Centre 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 CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, 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
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6785:2007: E
worldwide for CEN national Members.

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EN ISO 6785:2007 (E)






Foreword



The text of ISO 6785:2001 has been prepared by Technical Committee ISO/TC 34 "Agricultural
food products” of the International Organization for Standardization (ISO) and has been taken
over as EN ISO 6785:2007 by Technical Committee CEN/TC 302 "Milk and milk products -
Methods of sampling and analysis", the secretariat of which is held by NEN.

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 December 2007, and conflicting national
standards shall be withdrawn at the latest by December 2007.

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


Endorsement notice

The text of ISO 6785:2001 has been approved by CEN as EN ISO 6785:2007 without any
modifications.

2

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INTERNATIONAL ISO
STANDARD 6785
IDF
93
Second edition
2001-05-15
Milk and milk products — Detection of
Salmonella spp.
Lait et produits laitiers — Recherche de Salmonella spp.
Reference numbers
ISO 6785:2001(E)
IDF 93:2001(E)
©
ISO and IDF 2001

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ISO 6785:2001(E)
IDF 93:2001(E)
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© ISO and IDF 2001
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ii © ISO and IDF 2001 – All rights reserved

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ISO 6785:2001(E)
IDF 93:2001(E)
Contents Page
1 Scope . 1
2 Normative reference . 1
3 Terms and definitions . 1
4 Principle . 1
4.1 General . 1
4.2 Pre-enrichment in non-selective liquid medium . 1
4.3 Enrichment in selective liquid media . 1
4.4 Streaking out and recognition . 2
4.5 Confirmation . 2
5 Culture media, reagents and sera . 2
6 Apparatus and glassware . 12
7 Sampling . 13
8 Preparation of test sample . 13
9 Procedure . 13
9.1 Safety precautions . 13
9.2 Test portion and pre-enrichment . 13
9.3 Enrichment . 14
9.4 Streaking out and recognition . 14
9.5 Confirmation . 15
10 Control cultures . 18
11 Expression of results . 18
12 Safety precautions . 18
13 Test report . 19
Annexes
A Diagram of procedure . 20
B Specification for brilliant green. 21
C Standard method for streaking agar plates. 22
Bibliography. 23
© ISO and IDF 2001 – All rights reserved
iii

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ISO 6785:2001(E)
IDF 93:2001(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 3.
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 member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 6785�IDF 93 was prepared by Technical Committee ISO/TC 34, Food products,
Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with
AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International.
This second edition cancels and replaces the first edition (ISO 6785:1985), which has been technically revised.
Annexes A and B form a normative part of this International Standard. Annex C is for information only.
© ISO and IDF 2001 – All rights reserved
iv

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ISO 6785:2001(E)
IDF 93:2001(E)
Foreword
IDF (the International Dairy Federation) is a worldwide federation of the dairy sector with a National Committee in
every member country. Every National Committee has the right to be represented on the IDF Standing Committees
carrying out the technical work. IDF collaborates with ISO and AOAC International in the development of standard
methods of analysis and sampling for milk and milk products.
Draft International Standards adopted by the Action Teams and Standing Committees are circulated to the National
Committees for voting. Publication as an International Standard requires approval by at least 50 % of National
Committees casting a vote.
International Standard ISO 6785�IDF 93 was prepared by Technical Committee ISO/TC 34, Food products,
Subcommittee SC 5, Milk and milk products, and the International Dairy Federation (IDF), in collaboration with
AOAC International. It is being published jointly by ISO and IDF and separately by AOAC International.
All work was carried out by the Joint ISO/IDF/AOAC Action Team on Harmonization, of the Standing Committee on
Microbial methods of analysis, under the aegis of its project leader, Mr. H. Becker (DE).
This fourth edition cancels and replaces the third edition (IDF 93:1995).
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
INTERNATIONAL STANDARD
IDF 93:2001(E)
Milk and milk products — Detection of Salmonella spp.
1 Scope
This International Standard specifies a method for the detection of Salmonella spp. in milk and milk products.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent edition of the normative document indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 8261�IDF 122, Milk and milk products — General guidance for the preparation of test samples, initial suspensions
and decimal dilutions for microbiological examination.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
Salmonella
microorganisms which form typical colonies on solid selective media and which display the biochemical and
serological characteristics described when tests are carried out in accordance with this International Standard
3.2
detection of Salmonella
detection of the presence or absence of these microorganisms, in a particular mass or volume, when tests are
carried out in accordance with this International Standard
4 Principle
4.1 General
The detection of Salmonella necessitates four successive stages (see annex A).
4.2 Pre-enrichment in non-selective liquid medium
�
Inoculation of the pre-enrichment medium with the test portion, and incubation at 37 C for 16 h to 20 h.
4.3 Enrichment in selective liquid media
Inoculation of Rappaport-Vassiliadis modified magnesium chloride/malachite green medium and of selenite/cystine
medium with the culture obtained in 4.2.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
Incubation of the Rappaport-Vassiliadis modified magnesium chloride/malachite green medium in the water bath or
�
incubator (6.4) set at 41,5 C for 24 h and then a further 24 h.
�
Incubation of the selenite/cystine medium in the incubator (6.3) set at 37 C for 24 h and then a further 24 h.
4.4 Streaking out and recognition
From the cultures obtained (4.3), inoculation of two selective solid media (brilliant green/phenol red agar and any
other suitable solid selective medium).
NOTE Suitable media allow the recovery of lactose-fermenting Salmonella strains.
�
Incubation of the brilliant green/phenol red agar in the incubator (6.3) set at 37 C and examination after 20 h to 24 h
and, if necessary, again after 40 h to 48 h to check the presence of colonies which, from their characteristics, are
considered to be presumptive Salmonella.
Incubation of the second selective solid medium at the appropriate temperature and examination after the
appropriate time to check the presence of colonies which, from their characteristics, are considered to be
presumptive Salmonella.
4.5 Confirmation
Subculturing of colonies of presumptive Salmonella (4.4) and confirmation by means of appropriate biochemical and
serological tests.
5 Culture media, reagents and sera
In order to improve the reproducibility of the results, it is recommended that, for the preparation of culture media,
dehydrated basic components or dehydrated complete media are used. In that case, follow the manufacturer's
instructions rigorously.
Use only reagents of recognized analytical grade, unless otherwise specified.
�
The pH values given refer to a temperature of 25 C. Adjustments, if necessary, are made by adding either
hydrochloric acid [c (HCl)= 1 mol/l] or sodium hydroxide solution [c (NaOH)= 1 mol/l].
If not used immediately, store the prepared culture media and reagents under conditions that do not produce any
� �
change in their composition, in the dark at a temperature between 0 C and + 5 C, for no longer than 1 month,
unless otherwise stated.
5.1 Water
Use distilled or demineralized water or water of equivalent purity. The water shall be free from substances that might
inhibit the growth of microorganisms under the test conditions specified in this International Standard.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2 Culture media
5.2.1 Pre-enrichment medium: Buffered peptone water
5.2.1.1 Composition
Peptone 10,0 g
Sodium chloride (NaCl) 5,0 g
Disodium hydrogen phosphate dodecahydrate
(Na HPO ·12H O) 9,0 g
2 4 2
Potassium dihydrogen phosphate (KH PO ) 1,5 g
2 4
Water 1 000 ml
5.2.1.2 Preparation
7,0� 0,1
Dissolve the components in the water by heating. Adjust the pH so that after sterilization it is .
Transfer the medium in quantities of 225 ml into flasks (6.9) of capacity 500 ml (or multiples of 225 ml into flasks of
�
suitable capacity). Sterilize in the autoclave (6.1) set at 121 C for 15 min. Cool to room temperature.
5.2.2 First selective enrichment medium: Rappaport-Vassiliadis modified magnesium chloride/malachite
green medium (RVS broth)
5.2.2.1 Solution A
5.2.2.1.1 Composition
Enzymatic digest of soya 5,0 g
Sodium chloride (NaCl) 8,0 g
Potassium dihydrogen phosphate (KH PO ) 1,4 g
2 4
Dipotassium hydrogen phosphate (K HPO ) 0,2 g
2 4
Water 1 000 ml
5.2.2.1.2 Preparation
�
Dissolve the components in the water by heating to about 70 C. Prepare solution A on the day of preparation of the
complete RVS medium.
5.2.2.2 Solution B
5.2.2.2.1 Composition
Magnesium chloride hexahydrate (MgCl ·6H O) 400,0 g
2 2
Water 1 000 ml
5.2.2.2.2 Preparation
Dissolve the magnesium chloride in the water. As this salt is very hygroscopic, it is advisable to dissolve the entire
contents of MgCl ·6H O from a newly opened container. For instance, 250 g of MgCl ·6H O is added to 625 ml of
2 2 2 2
water, giving a solution of total volume of 795 ml and a concentration of about 0,3 g/ml of MgCl ·6H O.
2 2
Solution B can be stored in an airtight brown glass bottle at room temperature for at least 2 years.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.2.3 Solution C
5.2.2.3.1 Composition
Malachite green oxalate 0,4 g
Water 100 ml
5.2.2.3.2 Preparation
Dissolve the malachite green oxalate in the water.
Solution C can be stored in a brown glass bottle at room temperature for at least 8 months.
5.2.2.4 Complete medium
5.2.2.4.1 Composition
Solution A (5.2.2.1) 1 000 ml
Solution B (5.2.2.2) 100 ml
Solution C (5.2.2.3) 10 ml
5.2.2.4.2 Preparation
Add to 1 000 ml of solution A, 100 ml of solutionB and 10 ml of solution C. Adjust the pH, if necessary, so that after
sterilization it is 5,2� 0,1. Dispense 10 ml quantities of the thus-obtained solution into test tubes (6.9) or into sterile
flasks (6.8) of suitable capacity to obtain the portions necessary for the test. Sterilize in the autoclave (6.1) set at
�
115 C for 15 min.
� �
Store the prepared medium in the refrigerator at 3 C� 2 C.
5.2.3 Second selective enrichment medium: Selenite/cystine medium
WARNING — Extreme care should be taken with the laboratory use of selenite solutions because of their
potentially toxic effect. Do not pipette by mouth under any circumstances.
5.2.3.1 Base
5.2.3.1.1 Composition
Tryptone 5,0 g
Lactose 4,0 g
Disodium hydrogen phosphate dodecahydrate
(Na HPO ·12H O) 10,0 g
2 4 2
Sodium hydrogen selenite 4,0 g
Water 1 000 ml
5.2.3.1.2 Preparation
Dissolve the first three basic components in the water by boiling for 5 min. After cooling, add the sodium hydrogen
selenite. Adjust the pH, if necessary, to 7,0� 0,1. Do not sterilize.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.3.2 L-Cystine solution
5.2.3.2.1 Composition
0,1 g
L-Cystine
Sodium hydroxide solution,c (NaOH)= 1 mol/l 15 ml
Sterile water approx. 85 ml
5.2.3.2.2 Preparation
Add the components to a sterile 100 ml one-mark volumetric flask. Dilute to the mark with sterile water. Do not
sterilize.
5.2.3.3 Complete medium
5.2.3.3.1 Composition
Base (5.2.3.1) 1 000 ml
L-Cystine solution (5.2.3.2) 10 ml
5.2.3.3.2 Preparation
Add the L-cystine solution aseptically to the base. Adjust the pH, if necessary, to 7,0� 0,1. Dispense the medium
aseptically into sterile flasks of suitable capacity to obtain the portions necessary for the test.
The medium may be used until a red precipitate occurs.
5.2.4 First selective solid medium: Brilliant green/phenol red agar (Edel and Kampelmacher)
5.2.4.1 Base
5.2.4.1.1 Composition
Meat extract powder 5,0 g
Peptone 10,0 g
Yeast extract powder 3,0 g
Disodium hydrogen phosphate (Na HPO ) 1,0 g
2 4
Sodium dihydrogen phosphate (NaH PO ) 0,6 g
2 4
a
Agar 12 g to 18 g
Water 900 ml
a
Depending on the gel strength of the agar.
5.2.4.1.2 Preparation
Dissolve the components or the dehydrated complete base in the water by heating, if necessary. Adjust the pH, if
necessary, so that after sterilization it is 7,0� 0,1. Transfer the base to tubes (6.9) or flasks (6.8) of appropriate
�
capacity. Sterilize in the autoclave (6.1) set at 121 C for 15 min.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.4.2 Sugar/phenol red solution
5.2.4.2.1 Composition
Lactose 10,0 g
Sucrose 10,0 g
Phenol red 0,09 g
Water approx. 80 ml
5.2.4.2.2 Preparation
Dissolve the components in approximately 50 ml of water in a 100 ml one-mark volumetric flask. Dilute to the mark
�
with the water. Heat the solution in a water bath (6.5) set at 70 C for 20 min. Cool in another water bath (6.5) set at
�
55 C. Use the solution immediately after cooling.
5.2.4.3 Brilliant green solution
5.2.4.3.1 Composition
Brilliant green (see specification in annex B) about 0,5 g
Water 100 ml
5.2.4.3.2 Preparation
Dissolve the brilliant green in the water. Store the solution for at least one day in the dark to allow auto-sterilization to
occur.
5.2.4.4 Complete medium
5.2.4.4.1 Composition
Base (5.2.4.1) 900 ml
Sugar/phenol red solution (5.2.4.2) 100 ml
Brilliant green solution (5.2.4.3) 1ml
5.2.4.4.2 Preparation
Add the brilliant green solution (5.2.4.3) aseptically to the sugar/phenol red solution (5.2.4.2) cooled in a water bath
� �
(6.5) to 55C5. Add this to the base, preheated in the water bath to5 C, and mix. The temperature of the water bath
� �
should be kept between 50C5and5 C while mixing.
5.2.4.4.3 Preparation of the agar plates
Place in each of an appropriate number of large Petri dishes (6.12) about 40 ml of the freshly prepared complete
medium (5.2.4.4). If large dishes are not available, place about 15 ml of the medium in small Petri dishes (6.12).
Allow to solidify.
If prepared in advance, store the agar plates for no longer than 4h at room temperature or no longer than 1 week
� �
between 0 C and + 5 C.
Immediately before use, dry the agar plates carefully (preferably with the lids off and the agar surface downwards) in
�
the oven (6.2) set at 50 C or in the laminar airflow cabinet (6.2) until the surface of the agar is dry.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.5 Second selective solid medium
The choice of the second medium is left to the discretion of the testing laboratory.
5.2.6 Nutrient agar
5.2.6.1 Composition
Meat extract 3,0 g
Peptone 5,0 g
b
Agar 12 g to 18 g
Water 1 000 ml
b
Depending on the gel strength of the agar.
5.2.6.2 Preparation
Dissolve the components or the dehydrated complete medium in the water, by heating if necessary. Adjust the pH, if
necessary, so that after sterilization it is 7,0� 0,1. Transfer the culture medium into tubes (6.9) or bottles (6.8) of
�
appropriate capacity. Sterilize in the autoclave (6.1) set at 121 C for 15 min.
5.2.6.3 Preparation of agar plates
Transfer about 15 ml of the melted medium to sterile small Petri dishes (6.12) and proceed as in 5.2.4.4.3.
5.2.7 Triple sugar/iron agar (TSI agar)
5.2.7.1 Composition
Meat extract 3,0 g
Yeast extract 3,0 g
Peptone 20,0 g
Sodium chloride 5,0 g
Lactose 10,0 g
Sucrose 10,0 g
Glucose 1,0 g
Iron(III) citrate 0,3 g
Sodium thiosulfate 0,3 g
Phenol red 0,024 g
c
Agar 12 g to 18 g
Water 1 000 ml
c
Depending on the gel strength of the agar.
5.2.7.2 Preparation
Dissolve the components or the dehydrated complete medium in the water, by heating if necessary. Adjust the pH, if
necessary, so that after sterilization it is 7,4� 0,1. Dispense the medium in quantities of 10 ml into test tubes (6.9) of
�
diameter 17 mm to 18 mm. Sterilize in the autoclave (6.1) set at 121 C for 15 min. Allow to set in a sloping position
to give a butt of depth 2,5 cm and a slant of 4 cm to 5 cm.
© ISO and IDF 2001 – All rights reserved
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.8 Urea agar (Christensen)
5.2.8.1 Base
5.2.8.1.1 Composition
Peptone 1,0 g
Glucose 1,0 g
Sodium chloride 5,0 g
Potassium dihydrogen phosphate (KH PO ) 2,0 g
2 4
Phenol red 0,012 g
d
Agar 12 g to 18 g
Water 1 000 ml
d
Depending on the gel strength of the agar.
5.2.8.1.2 Preparation
Dissolve the components or the dehydrated complete base in the water, by heating if necessary. Adjust the pH, if
�
necessary, so that after sterilization it is 6,8� 0,1. Sterilize in the autoclave (6.1) set at 121 C for 15 min.
5.2.8.2 Urea solution
5.2.8.2.1 Composition
Urea 400 g
Water, to a final volume of 1 000 ml
5.2.8.2.2 Preparation
Dissolve the urea in the water. Sterilize by filtration and check the sterility. (For details of the technique of sterilization
by filtration, refer to any appropriate textbook on microbiology.)
5.2.8.3 Complete medium
5.2.8.3.1 Composition
Base (5.2.8.1) 950 ml
Urea solution (5.2.8.2) 50 ml
5.2.8.3.2 Preparation
�
Add the urea solution aseptically to the base, previously melted and then cooled in the water bath (6.5) to 45 C.
Dispense the complete medium in quantities of 10 ml into sterile tubes (6.9). Allow to set in a sloping position.
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ISO 6785:2001(E)
IDF 93:2001(E)
5.2.9 L-Lystine decarboxylation medium
5.2.9.1 Composition
L-Lystine monohydrochloride 5,0 g
Yeast extract 3,0 g
Glucose 1,0 g
Bromocresol purple 0,015 g
Water 1 000 ml
5.2.9.2 Preparation
Dissolve the components in the water, by heating if necessary. Adjust the pH, if necessary, so that after sterilization
it is 6,8� 0,1. Transfer the medium in quantities of 5 ml into narrow culture tubes (6.9). Sterilize in the autoclave (6.1)
�
set at 121 C for 15 min.
5.3 Reagents
5.3.1 Saline solution
5.3.1.1 Composition
Sodium chloride 8,5 g
Water 1 000 ml
5.3.1.2 Preparation
Dissolve the sodium chloride in the water, by heating if necessary. Adjust the pH so that after sterilization it is
7,0� 0,1 90 ml 100 ml
. Transfer quantities of the solution to flasks (6.8) or tubes (6.9) so that they will contain to after
�
sterilization. Sterilize in the autoclave (6.1) set at 121 C for 15 min.
5.3.2 Reagents for-galactosidase reaction
5.3.2.1 Toluene
5.3.2.2 Buffer solution
5.3.2.2.1 Composition
Sodium dihydrogen phosphate (NaH PO ) 6,9 g
2 4
e
Sodium hydroxide, 10 mol/l solution approx. 3 ml
Water approx. 50 ml
e
Depending on the volume necessary to adjust the pH.
5.3.2.2.2 Preparation
Dissolve the sodium dihydrogen phosphate in approximately 45 ml of water in a 50 ml one-mark volumetric flask.
Adjust the pH to 7,0� 0,1 with the sodium hydroxide solution. Dilute to the mark with water.
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ISO 6785:2001(E)
IDF 93:2001(E)
5.3.2.3 ONPG solution
5.3.2.3.1 Composition
 0,08 g
o-Nitrophenyl -D-galactopyranoside (ONPG)
Water 15 ml
5.3.2.3.2 Preparation
� �
Dissolve the ONPG in the water preheated to 50 C� 1 C. Cool the solution to room temperature.
5.3.2.4 Complete reagent
5.3.2.4.1 Composition
Buffer solution (5.3.2.2) 5ml
ONPG solution (5.3.2.3) 15 ml
5.3.2.4.2 Preparation
Add the buffer solution to the ONPG solution.
5.3.3 Reagents for Voges-Proskauer (VP) reaction
5.3.3.1 VP medium
5.3.3.1.1 Composition
Peptone 7,0 g
Glucose 5,0 g
Di
...