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126 SEcTioN ii Microbiology ` microbiology—basic bacteriology Microbiology ` microbiology—basic bacteriology
Properties of growth
media The same type of media can possess both (or neither) of these properties.
Selective media Favors the growth of particular organism while preventing growth of other organisms. Example:
Thayer-Martin agar contains antibiotics that allow the selective growth of Neisseria by inhibiting
the growth of other sensitive organisms.
Indicator (differential) Yields a color change in response to the metabolism of certain organisms. Example: MacConkey
media agar contains a pH indicator; a lactose fermenter like E coli will convert lactose to acidic
metabolites color change to pink.
Special culture requirements
bUg meDia UseD For isolatioN meDia coNteNts/otHer
+
H influenzae Chocolate agar Factors V (NAD ) and X (hematin)
N gonorrhoeae, Thayer-Martin agar Selectively favors growth of Neisseria by
N meningitidis inhibiting growth of gram ⊕ organisms
with Vancomycin, gram ⊝ organisms except
Neisseria with Trimethoprim and Colistin,
and fungi with Nystatin
Very Typically Cultures Neisseria
B pertussis Bordet-Gengou agar (Bordet for Bordetella) Potato extract
Regan-Lowe medium Charcoal, blood, and antibiotic
C diphtheriae Tellurite agar, Löffler medium
M tuberculosis Löwenstein-Jensen medium, Middlebrook
medium, rapid automated broth cultures
M pneumoniae Eaton agar Requires cholesterol
Lactose-fermenting MacConkey agar Fermentation produces acid, causing colonies to
enterics turn pink
E coli Eosin–methylene blue (EMB) agar Colonies with green metallic sheen
Brucella, Francisella, Charcoal yeast extract agar buffered with The Ella siblings, Bruce, Francis, a
Legionella, Pasteurella cysteine and iron legionnaire, and a pasteur (pastor), built the
Sistine (cysteine) chapel out of charcoal and
iron.
Fungi Sabouraud agar “Sab’s a fun guy!”
Aerobes Use an O 2 -dependent system to generate ATP.
Examples include Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, and Bordetella
pertussis.
Reactivation of M tuberculosis (eg, after immunocompromise or TNF-α inhibitor use) has a
predilection for the apices of the lung.
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