Dehydrated culture media
Sorbitol Peptone Broth And Bile Salts (PSB) ISO
For the selective enrichment of Yersinia enterocolitica.
- Cat. No.
- LC-1298
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- BAMISO 10273ISO 11133
Sorbitol Peptone Broth and Bile Salts (PSB) is a medium recommended by ISO 10273 for the selective enrichment of Yersinia enterocolitica in food samples. Outbreaks of gastroenteritis associated with Yersinia enterocolitica are increasing. Contaminated food products such as pork, beef, and raw and processed milk have been identified as sources of infection.
Key features
Applications
Selective enrichment of Yersinia enterocolitica.
Industry
Food.
Standards
BAM, ISO 10273, ISO 11133.
Preparation
31 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
Enzymatic digest of casein provides nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Potassium phosphates act as a buffer system. Sorbitol is the fermentable carbohydrate providing carbon and energy.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber |
| Final pH (25 °C) | 7.6 ± 0.2 |
| Amount per litre | 31 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Enzymatic digest of casein | 5 |
| Bile salts | 1.5 |
| Sodium chloride | 5 |
| Sodium dihydrogen phosphate | 1.2 |
| Sodium hydrogen phosphate | 8.23 |
| Sorbitol | 10 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 31 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. Dispense into appropriate containers and sterilize in autoclave at 121 °C for 15 minutes.
According to ISO 10273
Detection of Yersinia enterocolitica according to ISO 10273:
- Obtain the initial suspension. Add a test portion of 25 g or 25 mL to 225 g or 225 mL of Sorbitol Peptone Broth and Bile Salts (PSB) to obtain a tenfold dilution, and homogenize.
- Inoculate the suspension (direct plating) onto 2 to 4 selective agar plates of Yersinia Selective Agar (CIN).
- Transfer the initial suspension in the liquid enrichment medium PSB to the selective enrichment medium ITC (Irgasan Ticarcillin and Potassium Chlorate Broth) (LC-1361), and incubate the two enrichment liquid media at a temperature of 25 °C for 44 hours.
- Plate out the enrichment with KOH treatment (mixing 0.5 mL of enrichment in 4.5 mL of 0.5% KOH solution for 20 s) on plates of Yersinia Selective Agar (CIN).
- Incubate the plates of Yersinia Selective Agar (CIN) at 30 °C for 24 hours.
- Verify the colony morphology as presumptive pathogenic Y. enterocolitica by successive culturing on selective plates. Typical colonies of Y. enterocolitica will appear colorless, with dark red centers, like bull's eye, surrounded by a transparent border.
- Confirm the presence of pathogenic Y. enterocolitica species by biochemical or molecular confirmation test.
Quality control
According to ISO 10273
Incubation conditions: 25 ± 1 °C / 44 ± 4 h.
Inoculation conditions: target microorganisms (< 100 CFU) / non-target microorganisms (> 1000 CFU) / selectivity (10⁴-10⁶ CFU).
| Microorganism | Specification | Characteristic reaction |
|---|---|---|
| Yersinia enterocoliticaATCC 23715 + Escherichia coli ATCC 8739 + Pseudomonas aeruginosa ATCC 27853 | > 10 characteristic colonies on CIN Agar | Characteristic colonies according to CIN Agar |
| Yersinia enterocoliticaCECT 9144 + Escherichia coli ATCC 8739 + Pseudomonas aeruginosa ATCC 27853 | > 10 characteristic colonies on CIN Agar | Characteristic colonies according to CIN Agar |
Bibliography
- ISO 10273 Microbiology of food and animal feeding stuffs - Horizontal method for the detection of presumptive pathogenic Yersinia enterocolitica.
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