Dehydrated culture media
Nutrient Agar with Sodium Chloride ISO
For the confirmation of enterobacteria.
- Cat. No.
- LC-1355
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- ISO 21528
Nutrient Agar with Sodium Chloride is a medium recommended by ISO 21528 for the confirmation of Enterobacteriaceae.
Key features
Applications
Confirmation of enterobacteria.
Industry
Food.
Standards
ISO 21528.
Preparation
28 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Peptone and beef extract provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Bacteriological agar is the solidifying agent.
This medium is used after enrichment in BPW (LC-1402) and subculture in VRBG Agar (LC-1092).
Select well-isolated characteristic colonies from a plate of VRBG Agar incubated for 24 hours at 37 °C and inoculate in Nutrient Agar with Sodium Chloride. If more than one morphology is present in the colonies, select one colony of each morphology to subculture. After 24 ± 2 hours at 37 °C, select a well-isolated colony from each of the incubated plates for the biochemical confirmation tests.
If any of the selected typical colonies is oxidase-negative and glucose-positive, the tube from which the subculture was derived shall be regarded as being positive for Enterobacteriaceae.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber, slightly opalescent |
| Final pH (25 °C) | 7.0 ± 0.2 |
| Amount per litre | 28 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bacteriological agar | 15 |
| Beef extract | 3 |
| Sodium chloride | 5 |
| Enzymatic digest of animal tissues | 5 |
Preparation and use
Preparation
Suspend 28 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 47-50 °C, mix well and dispense into plates.
According to ISO 21528
For the purification of colonies in the detection and enumeration of Enterobacteriaceae according to ISO 21528:
- Select well-isolated characteristic colonies from a plate of VRBG Agar (LC-1092) incubated for 24 hours at 37 °C. If more than one morphology is present in the colonies, select one colony of each morphology to subculture.
- Inoculate in Nutrient Agar with Sodium Chloride.
- After 24 ± 2 hours at 37 °C, select a well-isolated colony from each of the incubated plates for the biochemical confirmation tests.
- If any of the selected typical colonies is oxidase-negative and glucose-positive, the tube from which the subculture was derived shall be regarded as being positive for Enterobacteriaceae.
Quality control
According to ISO 11133
Incubation conditions: Enterobacteriaceae, Salmonella (24 ± 2 h / 37 ± 1 °C) and Yersinia enterocolitica (24 ± 2 h / 30 ± 1 °C).
Inoculation conditions: productivity qualitative (10³-10⁴ CFU).
| Microorganism | Specification |
|---|---|
| Salmonella enteritidisATCC 13076 | Good growth (2) |
| Salmonella typhimuriumATCC 14028 | Good growth (2) |
| Yersinia enterocoliticaATCC 23715 | Good growth (2) |
| Escherichia coliATCC 25922 | Good growth (2) |
| Escherichia coliATCC 8739 | Good growth (2) |
| Yersinia enterocoliticaATCC 9610 | Good growth (2) |
Bibliography
- ISO 21528: Microbiology of the food chain - Horizontal methods for the detection and enumeration of Enterobacteriaceae.
- The Food Hygiene (England) (No. 2) Regulations 2005 Draft Statutory Instrument. England: HMSO; 2005.
- SANCO 4198/2004 rev. 19 (PLSPV/2001/4198/4198R19-EN.doc). Draft Commission Regulation on Microbiological Criteria for Foodstuffs. 2005.
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