Alkaline Peptone Water is used for detection of Vibrio species. It is also recommended by ISO Committee under the specification ISO 8914:1990.

Summary and Explanation

This Alkaline Peptone Water is a pre-enrichment medium specially suited and standardized for Vibrio cholera and vibrio species from food, water feces and for clinical studies. This medium has been recommended by APHA, ISO AOAC and FDA to increase the recovery of vibrio species in fecal material and other samples(3-7). Clinical materials containing small numbers of Vibrio should be inoculated into an enrichment medium prior to plating onto a selective medium, such as TCBS Agar (DM253). Further steps like plating onto a solid medium to study morphology, biochemical and serological properties are recommended in official methods. Clinical samples like swabs and faeces can be added directly to the medium as described by Janda et al.(1) This medium is recommended by APHA(4) for enrichment of Vibrio species from seafood, infectious materials and other clinical specimens such as faeces(5). Add 10 grams of seafood to 90ml of Alkaline Peptone Water and incubate for up to 18-20 hours at 37°C. Prolonged incubation will cause the suppressed contaminating organisms to develop(9) . Alkaline Peptone Water is a suitable enrichment broth for this purpose ( 1 – 3) . The relatively high pH of the medium (approx. 8.6) provides a favourable environment for the growth of Vibrios.

Principles of the Procedure

The original formula of Alkaline Peptone Water was developed by Shread, Donovan and Lee to be used as an enrichment broth for the cultivation of Aeromonas species(10) and Cruickshank reported that when the pH is increased, the medi um can be used to cultivate Vibrio species (1). Peptic digest of animal tissue provides nitrogenous, carbonaceous, and other important nutrients. The high concentration of sodium chloride promotes the growth of Vibrio cholerae. The relatively high pH value of the medium suppresses the accompanying microbial flora.