recentaboutlinksarchive
Information

Layout: Like a knife.
Best viewed: Mozilla Firefox.
Resolution: 1280X800.


glitter-graphics.com
Website created by:
Fazdly
Hanisah
Rizwanah
Keyuan
Siti Aisyah
Enjoy your stay (:

Any comments?


ShoutMix chat widget

Credits

Icon: LJ/sixthmile
Layout: tuesdaynight
Inspiration: DayBefore!Misery

selective and differential media - part 1
Written on: Tuesday, July 28, 2009
Time: 8:44 AM

DEFINITION:

•A selective media will permit the growth of certain organisms while preventing the growth of others. A differential media does not prevent growth of organisms but will cause certain colonies to develop differently from other organisms present.


selective media:

  • MSA



Mannitol Salt Agar (MSA) is a selective and differential medium. The high concentration of salt (7.5%) selects for members of the genus Staphylococcus, since they can tolerate high saline levels. Organisms from other genera may grow, but they typically grow very weakly.




MSA also contains the sugar mannitol and the pH indicator phenol red. If an organism can ferment mannitol, an acidic byproduct is formed that will cause the phenol red in the agar to turn yellow. Most pathogenic staphylococci, such as Staphylococcus aureus, will ferment mannitol. Most non-pathogenic staphylococci will not ferment mannitol.