Selective and Differential Media

Selective media: media that prevents some bacterias growth
ex: mannitol salt agar(only bacteria that can survive high salt can grow on MSA)

Differential media: media that lets you see whether bacteria can eat different things
ex: DNase agar; if bacteria can break down DNA, agar changes from blue-green to clear where bacteria are.

What is the unknown?
What abx is it:
susceptible to?
resistant to?

The bacteria was susceptible to all the abx (tetracycline, vanomycin, neomycin, amoxicillian, penicillin)
Susceptibility in or least to greatest: van, neo, pen, amox, and tetra
No Resistance

Selective and Differential Media:
- ability of media to allow, disallow growth of bact., differentiate bact. b/c of ingredients in agar.
ex: DNase agar contains DNA attached to methylgreen dye
- if agar turns colorless, it means bact. on it can break down DNA

ex: Mannitol Salt agar- less than 75% NaCl most bact. can't grow in high salt environment but S. aureus, other skin bacteria's can.

MSA: contains Mannitol agar will turn from pink to yellow. If bacteria on it can eat mannitol.

S. aureus: (+) growth in NaCl
(+) mannitol frementation

EMB: Eosin-Methylene Blue
- doesn't let gram (+) grow on it, b/c blue dye
- contains lactose
- if bact. on agar can ferment lactose, agar turns metallic green.

E. coli: (+) for lactose fermentation
gram (-)

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