Desoxycholate Agar is a differential medium primarily used for the isolation, enumeration, and differentiation of coliforms in dairy products. It also serves as a medium for isolating enteric pathogens from various specimens like rectal swabs and feces.

Key Features and Applications:

• Coliform Differentiation: Based on lactose fermentation, coliforms form pink colonies, while non-lactose fermenters appear as straw-colored colonies.
• Enteric Pathogen Isolation: Non-lactose fermenting enteric pathogens form colorless colonies. The medium’s selective agents (sodium desoxycholate) generally inhibit non-enteric, non-lactose fermenters.
• Methodology: Can be used with both pour-plate and surface inoculation techniques. An overlay of uninoculated agar in pour-plate methods aids in colony counting.
• Counting Coliforms in Dairy: Samples are mixed with cooled Desoxycholate Agar, allowed to solidify, overlaid, and incubated at 35°C for 18-24 hours. Dark red colonies $\ge$ 0.5mm are counted.
• Important Note: The selective agents may inhibit certain Escherichia coli strains, especially with the pour-plate method.

This medium provides a reliable method for the direct count of coliforms in dairy products and assists in the preliminary isolation of enteric bacteria.

Catalog: CM0163