TERGITOL 7 AGAR (acc. to NF EN ISO)

TERGITOL 7 AGAR (acc. to NF EN ISO)
INTENDED USE
Tergitol 7 Agar (NF EN ISO) is used for the detection and enumeration of coliform and heat-tolerant
coliform bacteria in drinking water, swimming water and surface water with the membrane filtration
method.
HISTORY
In 1946, Pollard showed the bactericidal action of Tergitol 7 against Gram-positive bacteria. The
medium was then developed by Chapman, whose enumeration of coliform bacteria were about 30%
higher than those done on other selective media. The formula was then modified by the same author
by adding TTC (triphenyltetrazolium chloride), which was found to be useful for the rapid recognition of
Escherichia coli and Enterobacter aerogenes, which produce yellow colonies surrounded by a yellow
halo, while other Gram-negative bacteria (including Proteus and Pseudomonas) give dark red colonies.
This medium is recommended in NF EN ISO 9308-1 standard for the detection and enumeration of
Escherichia coli and coliform bacteria in water samples, using the membrane filtration method.
PRINCIPLES
- Tergitol 7 inhibits Gram-positive bacteria, limits invasion by Proteus and favors recovery of coliform
bacteria.
- Coliform bacteria form colonies that are yellow or orange inside a yellow halo. The halo results from
the acidification of lactose under the membrane filter in the presence of a colored indicator,
bromthymol blue.
- Other strains form colonies whose red color is due to the reduction of TTC to insoluble formazan.
- Bacteria that do not ferment lactose form colonies surrounded by a blue halo.
PREPARATION
-
Suspend 51.1 g of dehydrated medium (BK123) in 1 liter of distilled or deionized water.
Slowly bring to boiling, stirring slowly until complete dissolution.
Dispense 100 mL in flasks.
Sterilize in an autoclave at 121°C for 15 minutes.
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INSTRUCTIONS FOR USE
Cool and maintain the medium at 44-47°C.
Aseptically add 1 mL of reconstituted TTC 12.5 mg Supplement (BS026) per vial.
Homogenize thoroughly.
Pour into sterile Petri dishes (the agar layer should be 5 mm thick).
Let solidify on a cold surface.
Aseptically filter a known volume of the sample to test through a membrane.( BM147 or BM093)
brought to room temperature, deposit the membrane on the surface of the agar, filtered side up and
making sure that the membrane and agar are in close contact.
- Incubate at (36  2)°C for (21  3) hours and (44  4) hours [if necessary, for plates not
demonstrating typical colonies after (21  3) hours].
-
RESULTS
Examine the membranes and consider as typical all lactose-positive bacteria, regardless of colony size,
if a corresponding yellow halo in the medium under the membrane is present.
Re-isolate a representative number of typical colonies onto a non-selective Tryptic Soy agar (BK047,
BM017, BM049 or BM050) and in Tryptophan broth (BK163 or BM076), in order to perform an oxidase
test, in addition to an indole test from tryptophan, in the context of the examinations described in NF
EN ISO 9308-1 of September 2000.
Count as coliforms all characteristic colonies that are oxidase-negative. All colonies having a negative
oxidase reaction, but indole positive, should be considered as Escherichia coli.
TYPICAL COMPOSITION of the complete media
(can be adjusted to obtain optimal performance)
For 1 liter of medium :
- Pancreatic digest of meat ..............................................................10.0 g
- Meat extract .....................................................................................5.0 g
- Yeast extract ....................................................................................6.0 g
- Lactose ..........................................................................................20.0 g
- Tergitol 7 ..........................................................................................0.1 g
- Bromthymol blue .........................................................................50.0 mg
- 2,3,5 triphenyltetrazolium chloride (TTC) ....................................25.0 mg
- Bacteriological agar .......................................................................10.0 g
pH of the ready to use medium at 25°C : 7.2 ± 0.2.
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QUALITY CONTROL
- Dehydrated medium : beige to greenish powder, free-flowing and homogeneous.
- Prepared medium (complete) : blue-green agar.
- Typical culture response after (21  3) hours of incubation at (36  2)°C :
Microorganisms
1
Escherichia coli
Escherichia coli
1
Staphylococcus aureus
2
1
2
Growth
(Productivity ratio PR / R2)
Acid production
66%  R2  150%
PR  70%
inhibited
positive
positive
RIVM WR1
ATCC® 25922
CIP 53.154
Productivity ratio R2 as described in NF T90-461
Productivity ratio PR as described in XP CEN ISO/TS 11133-2
STORAGE / SHELF LIFE
Dehydrated medium : 2-30°C.
- The expiration date is indicated on the label.
Prepared medium (benchmark value*) :
- Base media in vials : 6 months at 2-8°C.
- Complete media in plates : 30 days at 2-8°C.
Pre-poured media in plates,
- Store between 2 and 14°C, shielded from light.
- The expiration date is indicated on the label.
TTC 12.5 mg Supplement :
- Store between 2 and 8°C, shielded from light.
- The expiration date is indicated on the label.
PACKAGING
Code
Pre-poured media in Petri plates (Ø 55 mm) :
- 20 plates
- 120 plates
BM14708
BM09308
Dehydrated base medium (without TTC) :
- 500 g bottle
BK123HA
TTC 12.5 mg Supplement :
- 10 vial pack
BS02608
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PHOTO SUPPORT
Product reference : [BK123HA + BS02608], BM14708, BM09308
Media used for : Detection and enumeration of Escherichia coli and coliform bacteria in water.
Escherichia coli (on membrane)
Tergitol 7 agar with TTC (acc. to NF EN ISO)
Ref : BM14708
Incubation : 48 hours / 37°C
Characteristics : yellow-orange colonies on amber agar
(colony color due to fermentation of lactose, no TTC reduction).
BIBLIOGRAPHY
Pollard, A.L. 1946. A useful selective bactericidal property of Tergitol 7. Science, 103: 758-759.
Chapman, G.H. 1947. A superior culture medium for the enumeration and differentiation of coliforms. J. Bacteriol., 53: 504.
Chapman, G.H. 1951. A culture medium for detecting and confirming Escherichia coli in ten hours. Am. J. Publ. Health, 41:
1381.
Mossel, D.A.A. 1962. An ecological investigation on the usefulness of two pecific modifications of Eijkman’s test as an element
of the methods for the detecting of faecal contamination of foods. J. Appl. Bact., 25: 20-29.
Rodier, J. 1984. L’analyse de l’eau. Dénombrement des coliformes, coliformes fécaux, et Escherichia coli présumés. Méthode
de dénombrement par filtration sur membrane. Dunod 7ème Ed., 798-803.
NF EN ISO 9308-1 (T 90-414). Septembre 2000. Qualité de l’eau. Recherche et dénombrement des Escherichia coli et des
bactéries coliformes. Partie 1 : Méthode par filtration sur membrane.
XP CEN ISO/TS 11133-2 (V 08-104-2). Janvier 2004. Microbiologie des aliments. Guide pour la préparation et la production
des milieux de culture. Partie 2 : Guide général pour les essais de performance des milieux de culture.
NF T 90-461. Juillet 2001 et NF T 90-461/A1. Juin 2005. Qualité de l’eau. Microbiologie. Contrôle qualité des milieux de
culture.
*Benchmark value refers to the expected value under standard laboratory conditions following manufacturer’s instructions. It is provided as a guide only and no
warranty, implied or otherwise is associated with this information.
The information provided on the package take precedence over the formulations or instructions described in this document.
The information and specifications contained in this technical data sheet date from 2009-03-24.
They are susceptible to modification at any time, without warning.
Code document : BK123/A/2002-10 : 7.
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Tél : + 33 (0)3 44 14 33 33 – Fax : + 33 (0)3 44 14 33 34 – www.biokar-diagnostics.com