Which of the following is considered an undefined media?

Undefined media, also known as complex or non-synthetic media, are those that contain components whose precise chemical composition is not known. This often includes extracts from natural sources, such as yeast, beef, or peptone, which provide a mixture of nutrients necessary for growth but do not allow for complete control over the chemical environment.

Sabouraud Dextrose Agar is characterized as an undefined medium because it contains peptone and dextrose, the exact composition of which can vary. This media is primarily used to grow fungi and yeasts, taking advantage of the complex nutrient sources present that support the growth of these microorganisms.

In contrast, Mannitol Salt Agar and MacConkey Agar are considered defined media because their components and concentrations are more clearly specified and include selective additives to grow specific types of bacteria. Mannitol Salt Agar contains mannitol and a high concentration of salt to select for staphylococci, while MacConkey Agar contains peptones, bile salts, and indicators that selectively isolate Gram-negative bacteria while allowing the differentiation of lactose fermenters.

Thus, the identification of Sabouraud Dextrose Agar as an undefined medium is accurate due to its reliance on natural extracts for nutrient availability.