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24 Cards in this Set

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enriched media
basal growth media with one or more growth factors added (enrichments)
What are some growth factors?
blood, carbs, amino acids, vitamins, and nacl
what characterizes fastidious bacteria
the need for additional nutrients in their media/environment
what is an auxotroph?

for e.g.,
it is derived from a prototroph which grows on a basal media.

-a bacterium which has mutated and developed a specific growth requirement that it previously synthesized itself

e.g. Streptococcus
salt-loving bacterium;

e.g., Vibrionolipherocous
enrichment media
-suppresses normal flora while enhancing pathogen growth

-usually for stool specimens
What does a selective media do?
selects for the growth of some bacteria while inhibiting the growth of others.
Some general agents of a Selective media
Antibiotics, Dyes, Chemicals, pH changes
What is the purpose of a selective media?
to better identify a bacterium
What is the purpose of an Enteric Media?
to isolate pathogens of the intestine.
What are ALL enteric media selective for?
Gram negative bacilli
What does a Low selectivity Enteric media ALLOW to grow?

Moderately selective?

HIghly selective?
-All GNB, whether pathogen or not.

-Moderately inhibits some normal flora.

-Highly inhibits almost all normal flora
and sometimes the pathogen itself too!
What is the purpose of a differential media?
to differentiate between bacteria, based on some charactistic which is usually based upon a biochemical reaction.
What kind of media are pH indicators in, and what do they do?
in DIFFERENTIAL; they register the difference between bacteria.
what are the three main ways for bacteria to produce energy?

-Aerobic respiration

-Anaerobic respiration

break down of molecules into energy

buildup of molecules using energy
how to report hemolysis:

gamma - no hemolysis

alpha - incomplete hemolysis; green-brown discoloration

beta - complete hemolysis; clear, colorless zone around colony
why stab the plate for hemolysis?
so if colonies being streaked are oxygen labile they will have the correct atmosohere to grow in
most common types of enrichment media:
-GN broth
additives that make a medium selective:
dyes, bile salts, pH adjustments, antibiotics
CA stands for

and does what
chocolate agar

supports growth of fastidious bacteria
what plates are low selectivity?

how do they work?
LEMB and McConkey's.

allow all gnb to grow; do not select for enteric pathogens.
What plates are moderately selective?

How do they work?

they select for GNB, and contain chemicals that inhibit growth of normal gnb flora.
what plates are highly selective?

how do they work?
bismuth sulfite agar
brillian green agar

contain chemicals which inhibit virtually all enteric non-pathogens.