Artificial Media: Types Of Media

Question 0

Nutrient Media

Answer 0

More complex
Usually made of extracts of meat or soy beans
Example: nutrient broth, trypticase soy broth (or agar)

Question 1

Minimal Media

Answer 1

Simple and completely defined
Rarely used in the clinical lab
Example: tap water agar (used to identify aerobic actinomycetes)

Question 2

Enriched Media

Answer 2

A growth medium that contains added growth factors such as blood, vitamins, and growth factors
Example: blood agar, chocolate agar

Question 3

Selective Medium

Answer 3

Contains additives (e.g. Dyes or antibiotics) that inhibit some bacteria, but allow others to grow
Example: MacConkey agar, PEA agar

Question 4

Differential Medium

Answer 4

Allows visualization if metabolic differences between groups or species of bacteria
Example: a vast array of carbohydrate and amino acid containing media with pH indicators routinely used in conventional identification… Or the hemolysis seen on blood containing media
NOTE: a medium such as MacConkey is both differential AND selective. A formulation of MacConkey that does not include crystal violet is less selective but still differential

Question 5

Transport Medium

Answer 5

Preserves the viability of organisms but does not allow multiplication

Question 6

Why do you need a particular variety of medium?

Answer 6

1. Recovery of organisms from clinical material
   - concern for recovery of fastidious organisms
2. Isolation if multiple organisms from the same material
   - need to separate pathogens from endogenous flora, or separate multiple pathogens from each other
3. Identification of an organism
   - based largely on metabolic differences