Alkaline Peptone Water- Composition, Principle, Preparation, Results, Uses


Alkaline peptone water (APW) is a liquid medium that is used for the cultivation and enrichment of Vibrio species, especially Vibrio cholerae, the causative agent of cholera. Cholera is an acute diarrheal disease that can be fatal if left untreated. Vibrio cholerae is a gram-negative, comma-shaped bacterium that is found in aquatic environments, such as rivers, lakes, coastal waters and brackish water. Vibrio cholerae can also contaminate food and water sources, leading to outbreaks of cholera in humans.

Vibrio species are fastidious organisms that require specific conditions for optimal growth and survival. They are sensitive to acidic pH, high temperature and low salinity. Therefore, they need a medium that can provide them with a suitable environment for their growth and enrichment. Alkaline peptone water is one such medium that can meet these requirements. It has a high pH of 8.6, which inhibits the growth of most other bacteria that are present in the samples. It also contains 2% sodium chloride, which provides osmotic balance and enhances the growth of Vibrio species. Additionally, it contains peptone, which supplies nitrogen, carbon and other essential nutrients for the bacteria.

Alkaline peptone water is used as a pre-enrichment step before plating the samples onto solid media for isolation and identification of Vibrio species. It can also be used for direct microscopic examination of the samples using the hanging drop method. Alkaline peptone water is easy to prepare and use, and it has a long shelf life. It is widely used in microbiology laboratories, public health departments and food safety agencies for the detection and enumeration of Vibrio species from various sources.