Micro Lab Selective Media

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Micro Lab Selective Media
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Mannitol Salt Agar

• Contains mannitol (a carbohydrate), 7.5 sodium
  chloride (salt), and phenol red (pH indicator)
• High salt favors the growth of salt tolerant
  organisms (the staphylococci) and inhibits others
• Staphylococcus aureus can also ferment the
  mannitol and lowers the pH (yellow halo)
• Observe your MSA plate. Mark down growth or no
  growth, then fermented mannitol or did not
  ferment mannitol

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PEA-phenylethyl Alcohol Agar

• Allows growth of gram positives and stops or
  inhibits most gram negative
• Phenylethyl alcohol interferes with DNA synthesis
  in gram negative organisms
• Used to isolate staphylococcus and streptococcus
  and can screen out contaminants like E. coli and
  Proteus
• Observe your plate. Mark down growth or no
  growth (limited or poor growth)

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Columbia CAN with Sheep Blood

• Allows the growth of gram positive and inhibits
  the growth of most gram negative
• CAN acts as a selective agent by affecting
  membrane integrity and interfering with DNA
  replication.
• You can also observer hemolysis on this plate.
• Read through the bottom of your plate and see if
  it is clear (beta hemolysis), greenish (alpha
  hemolysis) or no change (gamma hemolysis)

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NEW material

• Get EMB/MAC agar and streak the plate on both
  sides of the plastic divide. This is for 4-4 and
  4-6
• Obtain a plate of Hektoen Enteric Agar (if
  available) and inoculate this plate too.
• HE is used to isolate Salmonella and Shigella
• You will observe these next week.