Alkaline peptone water is an enrichment medium used for Vibrio cholerae and other Vibrio The pH of the medium ranges from 8.6-9.0. The alkalinity of the medium favors the growth and multiplication of Vibrio species while inhibiting the growth of faecal coliforms and other commensals.

 Composition of alkaline peptone water

1000 ml of alkaline peptone water contains;

1. Peptone ………………………………..       10gm
2. Sodium chloride ……………………      10gm

• Distilled water ……………………      1000ml

Preparation of alkaline peptone water

1. Weigh the required amount of peptone (10gm) and Sodium chloride (10gm) and dissolve in 1000 ml of distilled water
2. ( OR dissolve 20 gm of alkaline peptone water broth in 1000ml of d/w according to manufacturer instruction)
3. Adjust the pH of medium to 8.6-9.0
4. Dispense the medium in 10ml amounts in screw cap bottles
5. Sterilize the bottles (with caps loosen) by autoclaving at 121°C for 25 minutes
6. Tighten the caps of the bottles after the medium has cooled to prevent change in pH
7. Label the bottle with date and batch number and store 4° Stored alkaline peptone medium can be used up to 2 years.

Uses of alkaline peptone water

1. It is an enrichment medium for Vibrio species.
   • Inoculate with 3-4 loopfuls of faecal sample in alkaline peptone broth and incubate at 37°C for 5-8 hours.
   • From surface of peptone broth subculture can be done on alkaline Nutrient agar or TCBS
2. It is a transport medium providing the transport time does not exceed 10 hours
   • Inoculate 1ml of fluid sample (water sample) or rectal swab on peptone water
   • The inoculated peptone water should reach laboratory within 10 hours

** Proteus species can contaminate alkaline peptone water

Alkaline peptone water: composition, preparation and uses

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