Differential Media

Various dyes, pH indicators, and other ingredients are included in differential plating media to serve as indicators of enzymatic activities and aid in identifying bacterial isolates.

For example in MacConkey agar, lactose fermenting colonies appear pink and lactose nonfermenting colonies appear pale or clear whereas the lactose fermenting colonies appear yellow in Hektoen-Enteric agar. This is because of the production of acids and subsequent changes in pH. As different pH indicators are used in these media, the colors of the colonies are different.

Tinsdale Agar: Composition, Preparation, Uses

Tinsdale Agar: Composition, Preparation, Uses

Tinsdale Agar is used for the selective isolation and differentiation of C. diphtheriae from diphtheroids.

DCA Agar: Composition, Colony Characteristics

DCA Agar: Composition, Colony Characteristics

Deoxycholate citrate agar is used for the selective isolation and differentiation of Salmonella and Shigella species.

Bismuth Sulfite Agar: Composition, Uses, Colony Morphology

Bismuth Sulfite Agar: Composition, Uses, Colony Morphology

Bismuth sulfite agar is a modification of original Wilson and Blair medium used for the isolation of Salmonella typhi and other salmonellae.

Chromogenic Culture Media: Principle, Composition, Results

Chromogenic Culture Media: Principle, Composition, Results

It contain chromogenic substrate which is utilized by the microorganisms to give colored colonies that is specific for each microorganism.

Salmonella-Shigella (SS) Agar

Salmonella-Shigella (SS) Agar

Salmonella-shigella (SS) agar is commonly used for the selective isolation and differentiation of Salmonella and Shigella.

CLED Agar: Composition, Uses, Colony Characteristics

CLED Agar: Composition, Uses, Colony Characteristics

Differential medium used for urine culture as it inhibits the swarming of Proteus and also supports the growth of gram-positive cocci.

Hektoen Enteric (HE) Agar: Composition, Uses

Hektoen Enteric (HE) Agar: Composition, Uses

Hektoen Enteric Agar (HE) is a selective and differential medium to isolate and differentiate Salmonella and Shigella from other Enterobacteriaceae.

TCBS Agar: Composition, Preparation, Uses

TCBS Agar: Composition, Preparation, Uses

TCBS agar is a selective as well as differential culture medium used for selective isolation and differentiation of Vibrio species.

EMB Agar: Composition, Principle, and Colony Morphology

EMB Agar: Composition, Principle, and Colony Morphology

Eosin methylene blue (EMB) agar is a selective and differential medium used to isolate fecal coliforms.

Blood Agar and Types of Hemolysis

Blood Agar and Types of Hemolysis

Blood agar is an enriched medium which supports growth of gram-positive cocci and differentiates them on the basis of hemolysis (α, β, or γ).

MacConkey Agar: Composition, Uses, Colony Characteristics

MacConkey Agar: Composition, Uses, Colony Characteristics

Selective (against gram-positive bacteria) and differential culture medium (LF and NLF), commonly used for the isolation of enterics.

Mannitol Salt Agar: Principle, Uses, and Results

Mannitol Salt Agar: Principle, Uses, and Results

Mannitol Salt Agar selects and differentiates Staphylococcus species. Staphylococcus aureus ferments mannitol and gives yellow colonies.