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Streptococcus lactis Differential Agar Base
Carbon Utilization Test#CC293D
Composition
| Ingredients | Gms/Litre |
|---|---|
| Nonfat (skim) milk | 10.000 |
| Peptonized milk | 2.500 |
| Dextrose | 5.000 |
| Agar | 15.000 |
| Final pH (at 25°C) | 6.6±0.2 |
**Formula adjusted, standardized to suit performance parameters
Directions
Suspend 32.5 grams in 1000 ml distilled water. Heat to boiling with stirring to dissolve the medium completely. Sterilize by autoclaving at 10 lbs pressure (115°C) for 12 minutes. Cool to 45°C and aseptically add (30 minutes steam-sterilized solutions) 10 ml of 10% potassium ferricyanide and 10 ml of citrate solution containing 0.25 g ferric citrate and 0.25 gram sodium citrate. Gently mix and pour into the sterile Petri plates. Dry the plates in dark for 24 hours at 30°C.
Principle And Interpretation
The lactic group of the genus Streptococcus originally included the species Streptococcus lactis and Streptococcus cremoris and a subspecies of S. lactis S. lactis subsp. diacetylactis. However, even in the 1970s workers were suggesting that S. lactis strains might be variants of S. diacetylactis that were unable to ferment citric acid, since citrate permease-negative strains of S. diacetylactis had been described. Streptococcus Lactis Differential Agar is formulated as described by Kempler and McKay (1) and is recommended for the differentiation of citrate utilizing lactic streptococci - Lactococcus lactis (Streptococcus lactis) subspecies diacetylactis from citrate non-utilizing Lactococcus lactis (Streptococcus lactis) and Lactococcus lactis (Streptococcus lactis) subspecies cremoris.
Non fat (skim) milk and peptonized milk in the medium provide nitrogen, vitamins and minerals necessary to support bacterial growth. Dextrose is the energy source.
Quality Control
Appearance
Off white to yellow homogeneous free flowing powder
Gelling
Firm, comparable with 1.5% Agar gel
Colour and Clarity of prepared medium
Light yellow coloured opaque gel forms with white precipitate in Petri plates
Reaction
Reaction of 3.25% w/v aqueous solution at 25°C. pH: 6.6±0.2
pH
6.40-6.80
Cultural Response
M925: Cultural characteristics observed after an incubation at 30°C for 18-48 hours with added 10% Potassium ferricyanide and citrate solution.
| Organism | Inoculum (CFU) | Growth | Recovery |
|---|---|---|---|
| Streptococcus cremoris ATCC 19257 | 50-100 | good-luxuriant | >=50% |
| Streptococcus lactis ATCC 8000 | 50-100 | good-luxuriant | >=50% |
| Streptococcus lactis subsp.diacetylactis | 50-100 | good-luxuriant | >=50% |
Storage and Shelf Life
Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label.
| Product Name | Streptococcus lactis Differential Agar Base |
|---|---|
| SKU | M925 |
| Product Type | Regular |
| Physical Form | Powder |
| Origin | Animal |
| Packaging type | HDPE |
| References | 1. Kempler G. M. and McKay L. L., 1980, Appl. Environ. Microbiol., 39:926. |
| Customized Product Available | No |



