Dehydrated culture media
OF Basal Medium (Hugh And Leifson)
For the identification of non-fermenting bacilli.
- Cat. No.
- LC-1500
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
OF Basal Medium (Hugh And Leifson) is a semisolid medium, prepared according to Hugh and Leifson's formula, and is used to determine the metabolism (oxidation, fermentation) of Gram-negative bacteria. It is useful for Pseudomonas, Salmonella, Shigella and Alcaligenes.
Key features
Applications
Differentiation of non-fermentative Gram-negative bacteria.
Industry
Antimicrobial susceptibility testing.
Preparation
9.8 g in one litre of distilled water; heat until dissolved, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Bromothymol blue is the pH indicator. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Dipotassium phosphate acts as a buffer system. Bacteriological agar is the solidifying agent.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige with a greenish tint |
| Color of the prepared medium | Green-bluish |
| Final pH (25 °C) | 7.1 ± 0.2 |
| Amount per litre | 9.8 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bromthymol blue | 0.03 |
| Bacteriological agar | 2.5 |
| Casein peptone | 2 |
| Dipotassium phosphate | 0.3 |
| Sodium chloride | 5 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 9.8 grams of the medium in one litre of distilled water. Heat with frequent agitation until dissolved. Sterilize in autoclave at 121 °C for 15 minutes. Add 10 mL of 10% glucose (or any suitable sugar) solution, sterilized by filtration, to 100 mL of liquid medium. Mix and aseptically dispense 5 mL per tube. If preferred, add 1.0 grams of carbohydrate directly to 100 mL of medium and sterilize in the autoclave at 118 °C for 10 minutes to avoid the degradation of the sugar.
Instructions for use
- Inoculate 2 fresh tubes by stabbing with a fresh culture of the organism under study. If the medium has been prepared and stored, remelt in a water bath to expel the dissolved gases.
- After inoculation, add a layer of 4 to 5 mm of paraffin oil to one of the tubes. It is not recommended to use mineral oil.
- Incubate both tubes at 35 °C for 48 hours or more, up to 7 days, with the caps loose.
- To facilitate the identification of Gram-negative non-fermenting bacilli, also use Indole Nitrate Medium (LC-1504).
Results:
- Fermentation: yellow color in both tubes with or without gas.
- Oxidation: yellow color only in the tube without oil.
- No oxidation/fermentation: no change in the color of the tubes. The carbohydrates have not been fermented or oxidized. Inert microorganisms, e.g. Alcaligenes faecalis.
Quality control
Microbiological test
Incubation conditions: 37 ± 1 °C / 48-72 h.
- K = alkaline, green (without change)
- A = acid, yellow
- G = gas, sometimes perceptible
| Microorganism | Specification | Characteristic reaction without sugar | Characteristic reaction with glucose |
|---|---|---|---|
| Shigella flexneriATCC 12022 | Good growth | Opened: K, closed: K | Opened: A, closed: A |
| Salmonella enteritidisATCC 13076 | Good growth | Opened: K, closed: K | Opened: AG, closed: AG |
| Escherichia coliATCC 25922 | Good growth | Opened: K, closed: K | Opened: AG, closed: AG |
| Pseudomonas aeruginosaATCC 27853 | Good growth | Opened: K, closed: K | Opened: K, closed: K |
| Alcaligenes faecalisATCC 8750 | Good growth | Opened: K, closed: K | Opened: K, closed: K |
Bibliography
- Hugh, R. and Leifson, E. J. Bact. 66:24-26. 1953.
- Lisenko J. Gen. Microbiol., 35:379, 1961.
- Edwards and Ewing Identification of Enterobacteriaceae. Burgess Publ. Co. Minneapolis, Minn., 1972.
What you receive
The product
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