Special culture requirements

This table outlines the special culture media used for isolating specific microorganisms and their contents. Each medium is designed to provide the optimal environment for the growth of specific bacteria or fungi by including essential growth factors and inhibitors.

Media Used for Bacterial Isolation

Bug	Media Used for Isolation	Media Contents / Key Notes
Haemophilus influenzae	Chocolate agar	Contains Factors V (NAD⁺) and X (hematin) to support growth.
Neisseria gonorrhoeae, Neisseria meningitidis	Thayer-Martin agar	Inhibits gram-positive organisms (vancomycin), gram-negative organisms except Neisseria (colistin, trimethoprim), and fungi (nystatin). Selectively cultures Neisseria.
Bordetella pertussis	Bordet-Gengou agar, Regan-Lowe medium	Bordet-Gengou contains potato extract. Regan-Lowe contains charcoal, blood, and antibiotics.
Corynebacterium diphtheriae	Tellurite agar, Löffler medium	Used to enhance the growth of C. diphtheriae.
Mycobacterium tuberculosis	Löwenstein-Jensen medium, Middlebrook medium	Contains ingredients like egg-based nutrients and antibiotics.
Mycoplasma pneumoniae	Eaton agar	Requires cholesterol for growth.
Lactose-fermenting enterics	MacConkey agar	Lactose fermentation produces acid, turning the colonies pink.
Escherichia coli	Eosin-methylene blue (EMB) agar	Produces colonies with a distinctive green metallic sheen due to lactose fermentation.
Brucella, Francisella, Legionella, Pasteurella	Charcoal yeast extract agar (buffered with cysteine and iron)	Supports growth with cysteine and iron.
Fungi	Sabouraud agar	Specialized media for fungi cultivation, commonly referred to as “Sab’s a fun guy!”

Media Used for Bacterial Isolation

Points to Remember

Chocolate agar: Provides Factors V and X necessary for the growth of Haemophilus influenzae.
Thayer-Martin agar: Selectively grows Neisseria species by inhibiting other bacteria and fungi.
Bordet-Gengou and Regan-Lowe media: Used for isolating Bordetella pertussis, with different compositions for optimal growth.
Tellurite and Löffler media: Enhance the isolation of Corynebacterium diphtheriae.
MacConkey agar: Lactose fermenters like Escherichia coli appear pink, useful for identifying enteric bacteria.
Charcoal yeast extract agar: Commonly used for Legionella, Brucella, Francisella, and Pasteurella due to the presence of cysteine and iron.
Sabouraud agar: A general medium for fungi, commonly used in mycology laboratories.

USMLE Step 1 Review Series

Curriculum

Special culture requirements

Media Used for Bacterial Isolation

Points to Remember

Bibliography Reference Links

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