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Alkaline peptone water is a commonly used enrichment medium for the search for Vibrio cholera, V. parahaemolyticus, V. vulnificus and other Vibrio spp. before selective enrichment and isolation (Ex: TCBS agar).
The pH of the medium varies from 8.6 to 9.0. The alkalinity of the environment promotes the growth and multiplication of Vibrio species while inhibiting the growth of faecal coliforms and other commensals.
Alkaline peptone water
Add 40g (20g of peptone and 20g of sodium chloride) to 1 liter of distilled water. Mix well, distribute in the final containers and sterilize in the autoclave at 121°C for 15 minutes.
Inoculate swab specimens directly into alkaline peptone water
Composition alkaline peptone water |
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---|---|---|---|
Ingredients | Gram/ liter | ||
Peptone | 20g | ||
Sodium Chloride | 20g | ||
Final pH (at 25°C) | 8.4±0.2 |
The pH of the medium varies from 8.6 to 9.0. The alkalinity of the environment promotes the growth and multiplication of Vibrio species while inhibiting the growth of faecal coliforms and other commensals.
Peptone provides essential vitamins, minerals, amino acids and nitrogen for growth needs. Sodium chloride provides essential electrolytes to maintain osmotic balance.
Clinical materials containing low numbers of Vibrio should be inoculated in enrichment medium before streaking on a selective medium, such as TCBS Agar. For biochemical identification, a pure culture is recommended.
Growth in the tubes is indicated by turbidity relative to an uninoculated (control) tube.