Differential Culture Media

Differential media are bacteriological growth media that contain specific ingredients that allow to distinguish selected species or categories of bacteria by visual observation. Differential means are used to distinguish between organisms or groups of closely related organisms.

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Examples of differential media :

• Mannitol salts agar (mannitol fermentation = yellow)
• Blood agar (various kinds of hemolysis i.e. α, β and γ hemolysis)
• Mac Conkey agar (lactose fermenters, pink colonies whereas non- lactose fermenter produces pale or colorless colonies.
• TCBS (Vibrio cholerae produces yellow colonies due to fermentation of sucrose)

Classification

• Distinguishes one microorganism type from another growing on the same media on a difference in the colony appearance
  • Color, shape, growth pattern
  • Dyes in the medium, pH indicators
• Eosin-methylene blue agar
  • Differential for lactose and sucrose fermentation
• MacConkey agar
  • Differential for lactose fermentation
• Mannitol salt agar
  • Differential for mannitol fermentation

Types of Culture Media :

There are some types of important culture or growth media used in microbiological laboratories:

• The Preservation Culture Media
• The Enrichment Culture Media
• Selective Culture Media
• Differential Culture Media
• Resuscitation Culture Media
• General Purpose Media

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