mannitol salt agar
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Why is this test performed?
For isolation of Staphylococcus aureus.
How is the agar inoculated?
Spot inoculated with the test organisms.
What special ingredients are added to this agar in order to perform the test?
Mannitol, sodium chloride & phenol red (indicator).
How can we tell the difference btwn positive & negative results? What do they tell us about the bacteria used?
- POSITIVE: Turns yellow with halo.
- NEGATIVE: No growth
- Poor growth-not staphylococcus.
- Good growth-staphylococcus
- Yellow growth-S aureus
- Red growth-staphylococcus (not s. aureus)
Define complex media.
A medium used in genetic experiments that supplies all nutrients for growth required by prototrophs & auxotrophs.
Define selective media.
Selective media is a type of media that selects for the growth of one type of organism, while inhibiting the growth of others.
Define differential media.
Differential media distinguishs one microorganism type from another growing on the same media.
Which types of media is MSA?
- It's both selective & differential.
- It's selective for Gram + Staphylococcus. Sodium chloride makes it selective.
- It's differential b/c it distingueshes btwn staphylococcus specias (s. aureus). Mannitol makes it differential. If the staph species ferments mannitol & produces acid, it will turn the ph indicator yellow.
What types of bacteria can & cannot grow on this media?
- CAN GROW: Gram +
- CAN'T GROW: Gram -
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