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Material Safety Data Sheet

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Organisms

Organisms this product works with:

Dehydrated Culture Media

TERGITOL-7 AGAR

Code: CM0793

A selective medium for the detection and enumeration of coliforms.

Typical Formula*

gm/litre

Peptone

10.0

Yeast extract

6.0

Meat extract

5.0

Lactose

20.0

Bromothymol blue

0.05

Tergitol-7

0.1

Agar

13.0

pH 7.2 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards 

TTC Solution (SR0148) is supplied as 2ml of filtered 0.125% aqueous solution of tri-phenyltetrazolium chloride (TTC).

Directions
Suspend 54.15g in 1 litre of distilled water. Bring to the boil to dissolve completely. Dispense in 100ml volumes and sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C and add the contents of 1 vial of SR0148. Mix well and pour into sterile Petri dishes.

Description
Tergitol-7 Agar is a selective and differential medium for the detection and enumeration of coliforms in food and water samples.

Tergitol-7 Agar is based on the formulation described by Chapman1 and is recommended for the selective isolation and differentiation of the coliform group. The use of Tergitol-7 as a selective agent had been described earlier2.

The addition of tri-phenyltetrazolium chloride (TTC)3 allows earlier recognition and identification of Escherichia coli and Enterobacter aerogenes. This medium has been recommended for examining foodstuffs for faecal contamination4 and has been successfully used in routine water analysis5.

Tergitol-7 inhibits Gram positive organisms and minimises the swarming of Proteus allowing superior recovery of coliforms. Fermentation of lactose is seen by a change in colour of the pH indicator bromothymol blue. TTC is rapidly reduced to insoluble red formazan by most coliform organisms except Escherichia coli and Enterobacter aerogenes, thus allowing easy differentiation. Tergitol-7 Agar is quoted in the EU Directive for the detection and enumeration of coliforms in drinking water6.

Technique
Inoculate by spreading the sample on the surface of the agar. Incubate at 35°C for up to 24 hours.

Escherichia coli

Yellow colonies with yellow zone
Sometimes with rust coloured centre

Enterobacter/Klebsiella species

Greenish/yellow colonies

Salmonella species

Red colony with bluish zone

Shigella species

Red colony with bluish zone

Proteus species

Red colony with bluish zone

Pseudomonas species

Red colony with bluish zone

Gram positive bacteria

No growth to slight growth


Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Appearance
Dehydrated medium: Pale green coloured, free-flowing powder
Prepared medium: Dark green coloured gel

Quality control

Positive control:

Expected results

Escherichia coli ATCC® 25922 *

Good growth; yellow-orange coloured colonies with yellow zone

Negative control:

 

Staphylococcus aureus ATCC® 25923 *

Inhibited or no growth

* This organism is available as a Culti-Loop®

Precautions
Tergitol-7 Agar is designed for early detection of Escherichia coli i.e. 6-10 hours incubation3.
Incubation at 44°C has been recommended 4,5.

References
1. Chapman G. H. (1947) J. Bact. 53. 504.
2. Pollard A.L. (1946) Science 103. 758-759.
3. Chapman G.H. (1951) Am. J. Pub. Hlth 41. 1381.
4. Mossel D. A. A. (1962) J. Appl. Bact. 25. 20-29.
5. Kulp W., Mascoli C., Tavshanjian O. (1953) Am. J. Pub. Hlth 43. 1111-1113.
6. E.U. (1998) 98/83/EC of Council of 3rd of November 1998 on the quality of water intended for human consumption. Off. J. Eur. Commun., L3330, 32-54.

 
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