Biochemical Tests

Biochemical Tests

1. Mannitol Salt Agar

   • Selective Medium
     • Gram +
       • Staphylococcus
       • Enterococcus
   • Differentiates between organisms who can fermentate mannitol
     • Organisms who ferments mannitol
       • Drops ph level
         • Phenol red color to yellow
     • Organisms who can't
       • Produce red colonies

2. Eosin Methylene Blue Agar

   • Slightly selective
     • Gram - enteric bacteria
   • Differental Component
     • Organisms that can ferment lactose
       • Vigorous: purple-black colonies, metallic sheen
       • Less aggressive: pink to purple
     • Organisms that Can't
       • Colonies are colorless or blue

3. Phenol Red Broth

   • Differental
     • Detect Fermentation of specific carbs
       • Glucose
       • Sucrose
       • Organisms ferments carbs
         • Phenol Red to yellow
       • Determines production of gas

4. Methyl Red and Voges-Proskauer Tests

   • MR
     • Can the organism ferment mixed acid?
       • Positive: Red color
   • VP
     • Can the organism ferment sugars to produce acetoin and 2,3 butanediol?
       • Positive: Red Color

5. Catalase Test

   • Detects the presence of catalase enzyme
     • H202 -> H20 + 02
     • Positive: Bubbles

6. Oxidase Test

   • Detects cytochrome c oxidase
     • BBL Dry slide
       • 20 Sec
         • Positive: Pink-Blue
     • Found in ETC in some bacteria

7. Nitrate Reduction Test

   • Does the organism preform nitrate respiration?
     • Any bubbles?
       • No? Add nitrate reagents A and B
         • Positive: Red Color
           • Reduction of nitrate to nitrite
         • No color chage: Add zinc dust
           • Positive: No color change
             • nitrate reduced to some other nitrogenous products
           • Negative: Red color change
   • Differential
     • Partial or Complete?

8. Citrate Test

   • Simmons Citrate Agar
     • defined medium
       • citrate and ammonium phosphate
     • If organism uses citrate
       • alkalinize the medium
         • Green to blue
     • Differental
       • Gram -

9. Urease Test

   • detects the production of ammonia
     • Urease breaksdown urea to CO2 and NH3
       • Raises Ph
       • Positive: Pink

10. SIM Medium

    • Differential
      • Sulfur
        • Organism produce H2S?
          • Black precipitate
            • Ferric Sulfide FeS
      • Indole
        • O with tryptophanase
          • breaking down tryptophan
            • releasing indole
              • Adding Kovac reagent
                • Positive: Red Color
      • Motility