Purple Broth w/Mannitol and Durham Tube 8mL, 10/Pk

Purple Broth with Mannitol is a differential medium used to determine if a microorganism can ferment the sugar alcohol Mannitol. This test is a valuable tool in the identification of various bacteria, particularly Staphylococci and certain Enterobacteriaceae.

The Test Principle:

1. Substrate (Mannitol): The medium contains Mannitol as the sole fermentable carbohydrate source.

2. pH Indicator (Bromocresol Purple):

   • Purple: The medium starts at a neutral pH (6.8). A purple result after incubation indicates the organism cannot ferment Mannitol (Negative).

   • Yellow: If the organism ferments Mannitol, it produces acidic byproducts that lower the pH to 5.2, turning the medium Yellow (Positive).

3. Durham Tube: An inverted glass vial traps any gas produced during fermentation.

Key Applications:

• Staphylococcus Differentiation: This test helps distinguish the pathogenic Staphylococcus aureus (typically Mannitol Positive/Yellow) from the non-pathogenic Staphylococcus epidermidis (typically Mannitol Negative/Purple).

• Enteric Identification: Used alongside other carbohydrate broths to build a metabolic profile for identifying Gram-negative rods.

Interpreting Results:

• Positive : Yellow broth + Gas bubble in Durham tube.

• Positive : Yellow broth + No gas bubble (Acid production only).

• Negative : Purple broth (No acid or gas).

• Specific Differentiation: Critical for identifying S. aureus.

• Gas Detection: Durham tube confirms aerogenic fermentation.

• Clear Readout: Distinct Purple-to-Yellow color change.

• Stable Indicator: Bromocresol Purple resists false positives from weak acid producers.

• Format: Sterile 8mL screw-cap tubes with inverted Durham tubes in a 10-pack.

Read Less