Selectvie and Differential Media- King 2026

lab 6

How is mannitol salt agar (MSA) selective? Include the ingredient that makes it selective

MSA is selective because it contains 7.5% sodium chloride, which inhibits most bacteria except staphylococci.

How is mannitol salt agar (MSA) differential? Include the ingredient that makes it differential.

MSA is differential because it contains mannitol and the pH indicator phenol red, which detects mannitol fermentation.

What growth pattern does Staphylococcus epidermidis show on MSA?

Staphylococcus epidermidis grows but does not ferment mannitol, so the medium remains red.

What growth pattern does Staphylococcus aureus show on MSA?

Staphylococcus aureus ferments mannitol, turning the medium yellow

What is blood agar

Blood agar is an enriched and differential medium containing sheep blood used to detect hemolysis patterns

What is hemolysis?

Hemolysis is the breakdown of red blood cells by bacterial enzymes

What is alpha hemolysis?

Alpha hemolysis is partial RBC breakdown, producing a greenish or brownish discoloration around colonies.

What is beta hemolysis?

Beta hemolysis is complete RBC breakdown, producing a clear zone around colonies.

What is gamma hemolysis?

Gamma hemolysis is no hemolysis and no change to the medium around colonies

What must you be able to do with hemolysis on blood agar?

Recognize alpha, beta, and gamma hemolysis patterns on blood agar plates.

what is this

Escherichia coli

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Enterobacter aerogenes

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Pseudomonas Aeruginosa

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staphylococcus aureus

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staphylococcus epidermidis

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alpha hemolysis

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beta hemolysis

What is this

gamma hemolysis/ non-hemolytic