## Enriched Media: Composition and Function **Key Point:** Enriched media supplement a basal medium with nutrient-rich substances (blood, serum, egg, etc.) to support fastidious organisms. They are NON-selective — they do NOT inhibit any particular group of bacteria. Option 2 incorrectly describes enriched media as having inhibitory properties. ### Enriched Media Characteristics | Feature | Details | |---------|----------| | **Purpose** | Provide additional nutrients for fastidious (nutritionally demanding) organisms | | **Supplements** | Whole blood, defibrinated blood, serum (sheep, horse, rabbit), egg yolk, chocolate (lysed RBCs) | | **Selectivity** | NONE — enriched media are non-selective and support growth of many organisms | | **Differentiation** | Some enriched media can be differential (e.g., blood agar shows hemolysis patterns) | ### Common Enriched Media - **Blood agar** — Contains 5% sheep blood; supports fastidious organisms; differential (hemolysis patterns) - **Chocolate agar** — Lysed RBCs release nutrients (X factor = hemin, V factor = NAD); for Haemophilus, Neisseria - **Löffler's serum medium** — Contains coagulated serum; enriches for Corynebacterium diphtheriae - **Egg-based media** — Ogawa, Lowenstein-Jensen (for Mycobacterium tuberculosis) **High-Yield:** Enriched media ≠ Selective media. Enriched media ADD nutrients but do NOT inhibit organisms. Selective media INHIBIT unwanted organisms. **Mnemonic:** **ENriched = Extra Nutrients** — think of enriched media as "feeding" fastidious organisms, not "filtering" them. **Warning:** Do NOT confuse enriched media with selective media. Enriched media are permissive; selective media are restrictive.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.