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Principle
- Selenite F Broth is composed of tryptone, lactose, sodium selenite, and sodium phosphate. Tryptone provides nitrogen and amino acids. Lactose is a fermentable carbohydrate.
- Sodium selenite is a selective agent and inhibits the growth of gram-positive and many gram-negative organisms. Although sodium selenite is reduced by bacterial growth, and rise in pH takes place which leads to a decrease in the selectivity of selenite. Since lactose is added into the medium, due to lactose fermentation acid is produced and maintains neutral pH.
- The decrease in pH due to reduction of selenite is compensated by the acid produced by the lactose fermentation. Sodium phosphate provide phosphate for growth and helps in the maintenance of pH of the medium.
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