Dehydrated culture media
Buffered Peptone Water ISO
Recommended as a diluent for the homogenization of samples in the microbiological analysis and for the pre-enrichment of Enterobacteriaceae and Salmonella.
- Cat. No.
- LC-1402
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
- Standards
- BAMISO 11133ISO 11290ISO 19250ISO 21528ISO 6579ISO 6887
- Also available
- Dehydrated medium, 1 format (LC-1401)
- Also available
- Ready-to-use medium, 7 formats (LC-4250)
- Also available
- Ready-to-use medium, 2 formats (LC-4643)
Buffered Peptone Water is a non-selective medium recommended as a pre-enrichment medium by the ISO 6579 and ISO 19250 standards for Salmonella detection in food and water respectively and by the ISO 21528 standard for Enterobacteriaceae detection.
Key features
Applications
Enrichment of enterobacteria and Salmonella, diluent (general use).
Industry
Cosmetics, food, pharmaceutical/veterinary, water.
Standards
BAM, ISO 11133, ISO 11290, ISO 19250, ISO 21528, ISO 6579, ISO 6887.
Preparation
20 g in one liter of distilled water; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
A feature common to all selective media is that sublethally injured organisms are not generally detected and therefore a recovery step must be included in examination procedures. This is of importance, particularly in the food industry, as various processes such as heat, desiccation, preservation processes, pH changes, etc., cause sublethal injuries to Salmonella. The broth is rich in nutrients and produces high resuscitation rates for sublethally injured bacteria and intense growth.
Changes in pH may cause damage to bacterial growth. Buffered Peptone Water maintains a high pH over the enrichment period via the phosphate buffer system and allows repair of injured cells sensitive to low pH. Pancreatic digest of casein provides nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance.
Salmonella can be present in food and water in small numbers and are usually found with considerably larger numbers of other Enterobacteriaceae or other families. Pre-enrichment is necessary to allow the detection of small numbers of Salmonella or injured Salmonella.
Buffered Peptone Water is also recommended by ISO 6887 as a diluent for all enumerations of microorganisms and by ISO 11290 as a diluent for Listeria monocytogenes enumeration.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | White cream, slightly toasted |
| Color of the prepared medium | Light amber |
| Final pH (25 °C) | 7.0 ± 0.2 |
| Amount per litre | 20 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Enzymatic digest of casein | 10 |
| Potassium dihydrogen phosphate | 1.5 |
| Sodium chloride | 5 |
| Di-sodium hydrogen phosphate | 3.5 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 20 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 6579
For pre-enrichment of Salmonella spp. in food, animal feed, animal faeces, and environmental samples according to ISO 6579:
- Inoculate the Buffered Peptone Water with the sample or dilutions, and incubate at 34-38 °C for 18 h.
According to ISO 19250
For pre-enrichment of Salmonella spp. in water samples according to ISO 19250:
- Inoculate the Buffered Peptone Water with the sample or dilutions, and incubate at 36 ± 2 °C for 18 ± 2 h.
According to ISO 21528
For the pre-enrichment of Enterobacteriaceae according to ISO 21528:
- Inoculate Buffered Peptone Water (BPW) with the portion to be tested and incubate at 37 °C for 48 hours.
According to ISO 11290
For the dilution stage in the Listeria enumeration method according to ISO 11290:
- Prepare an initial suspension 1:10 of sample and Buffered Peptone Water for analysis. Listeria 1/2 Fraser Broth (LC-1183) can be used as a diluent if the detection and enumeration procedures are carried out simultaneously.
Quality control
According to ISO 11133
Incubation conditions: Escherichia coli ATCC 8739 according to ISO 6887 (20-25 °C / 45 min-1 h) / Staphylococcus aureus ATCC 25923 according to ISO 6887 (20-25 °C / 45 min-1 h) / Listeria monocytogenes ATCC 13932 according to ISO 11290 (1 h ± 5 min / 20 ± 2 °C).
Escherichia coli ATCC 8739 according to ISO 21528 (37 ± 1 °C / 18 ± 2 h) / Salmonella enteritidis ATCC 13076 according to ISO 21528 (37 ± 1 °C / 18 ± 2 h) / Salmonella Typhimurium ATCC 14028 according to ISO 21528 (37 ± 1 °C / 18 ± 2 h) / Salmonella Typhimurium ATCC 14028 according to ISO 6579 (34-38 °C / 18 ± 2 h) / Salmonella enteritidis ATCC 13076 according to ISO 6579 (34-38 °C / 18 ± 2 h) / Salmonella Typhimurium ATCC 14028 according to ISO 19250 (36 ± 2 °C / 18 ± 2 h) / Salmonella enteritidis ATCC 13076 according to ISO 19250 (36 ± 2 °C / 18 ± 2 h).
Inoculation conditions: dilution (10⁴ CFU) / productivity qualitative (< 10² CFU).
Reference media: TSA.
| Microorganism | Specification |
|---|---|
| Salmonella enteritidisATCC 13076 | Turbidity (1-2) for the productivity test |
| Listeria monocytogenes 4bATCC 13932 | ± 30% of original count for the dilution test |
| Salmonella typhimuriumATCC 14028 | Turbidity (1-2) for the productivity test |
| Staphylococcus aureusATCC 25923 | ± 30% of original count for the dilution test |
| Escherichia coliATCC 8739 | ± 30% of original count for the dilution test / Turbidity (1-2) for the productivity test |
Bibliography
- M.R. Pascual Anderson (1982) Techniques for Microbiological Analysis of Foods and Drinks, CeNAN.
- ISO 6579. Microbiology of food stuff for humans and animals. Horizontal method to detect Salmonella spp.
- ISO 19250 Water quality - Detection of Salmonella spp.
- ISO 6887 Microbiology of the food chain - Preparation of test samples, initial suspension and decimal dilutions for microbiological examination.
- ISO 11290 Microbiology of the food chain - Horizontal method for the detection and enumeration of Listeria monocytogenes and of Listeria spp.
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