Slanetz-Bartley Medium w/o TTC

Burkwall and Hartman demonstrated that the addition of 0.5 mL of Tween 80 and 20 mL of a 10% sodium carbonate or bicarbonate solution to each liter of the medium was valuable when investigating enterococci in frozen foods.

Tryptose provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly of the B-group. Glucose is the fermentable carbohydrate providing carbon and energy. Dipotassium phosphate is a buffer. Sodium azide inhibits Gram-negative bacteria. Triphenyltetrazolium chloride is reduced to formazan by the enterococci. Bacteriological agar is the solidifying agent.

The ISO 7899-2 standard recommends this medium for the enumeration of enterococci in water systems. Water is filtered through a membrane, which is then placed on the surface of a plate of Slanetz-Bartley Medium. The plate is incubated at 36 ± 2 °C for 44 ± 4 hours. The membrane is examined with a magnifying lens under good light and all red or brown colonies are counted as presumptive enterococci.

With a positive presumptive result, the membrane with the typical colonies is transferred to a dish with Bile Esculin Azide Agar (LC-1005), pre-warmed to 44 °C. The plates are incubated at 44 ± 0.5 °C for 2 hours. After incubation, typical colonies (brown-black surrounding the medium) are counted as intestinal enterococci.

This medium also complies with the recommendations of the British Ministry of Health - Report 71, and the German DIN Regulations 10181 and 10160 for the examination of milk, meat and meat products.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Suspend 41.4 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to 50-60 °C and, if desired, aseptically add 2 vials of TTC 1% Supplement (LC-6030), previously reconstituted in 5 mL of sterile distilled water.

According to ISO 7899-2

For the detection and enumeration of enterococci according to ISO 7899-2:

1. Filter a measured volume of water through a membrane filter.
2. Place the membrane on a Slanetz-Bartley Medium plate.
3. Incubate at 36 ± 2 °C for 44 ± 4 h.
4. Transfer the membrane with characteristic colonies previously incubated in the Slanetz-Bartley medium, without inverting the membrane, to a plate with Bile Esculin Azide Agar (LC-1005), pre-heated to 44 °C.
5. Incubate at 44 ± 0.5 °C for 2 hours.
6. Read the plate immediately.
7. It is considered that the typical colonies that show a brown-black color in the surrounding medium give positive reactions and are counted as intestinal enterococci.

• Slanetz L.W. and Bartley C.H. 1957. J. Bact. 74; 591-595.
• ISO 7899-2. Water quality - Detection and enumeration of intestinal enterococci - Part 2: Membrane filtration method.
• Nordic Committee of Food analysis 1968 Leaflet 68.
• Department of Health and Social Security report 711982.
• The Bacteriological examination of drinking water supplies, HMSO, London.