BIOL 362 Unknown Project

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Lab-DifofGramcocci2011.ppt
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Differentiation of
Gram (+) cocci

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Mannitol Salt Agar

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Gram Stains

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Mannitol Salt agar

  • Selective media
  • Selects for members of the Staphylococci
  • 7.5% NaCl

  • Differential Media
  • Carbohydrate source of mannitol
  • Phenol red indicator
  • Fermentation of mannitol = acid = yellow

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Mannitol salt agar

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Catalase

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Catalase

(-)

+

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Hemolysins

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Hemolysins

  • Checked after growth on sheep red blood cell agar
  • 3 kinds of hemolysis:

  • a-greenish/brownish zone around colonies; not true hemolysis but discoloration of rbcs

  • b-zone of rbc hemolysis or clearing; due to the production of streptolysin O or streptolysin S from Streptococcus sp. or hemolysins from Staphylococcus aureus

  • g- no hemolysis

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Staphylococcus epidermidis

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Hemolysins

Coagulase

  • 1) Grow the organism in a tube of tryptic soy broth (TSB). Add to a tube with citrated rabbit plasma and incubate at 37C for 24 hours:

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Coagulase Test (Labeled view)

American Society For Microbiology ©

2) Put the organism to be tested on a slide and add a drop of rabbit plasma. Rotate the slide and look for clumps.

Coagulase

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(+)

(-)