Bacterial Culture Flashcards
What is a culture medium?
A water solution of various nutrients that encourage the growth or organisms
What does a culture medium generally contain?
3
Energy
Carbon, nitrogen and other essential nutrients
Growth factors (may be added to encourage the growth of a particular fastidious organism)
What two forms can culture medias come in?
Liquids or gels
What does the success of culture depend on?
Selection of appropriate culture media
What are the five different types of medias?
General purpose media
Enriched media
Selective media
Differential media
Selective and differential media
Give an example of a general purpose media.
Horse blood agar
How is horse blood agar a general purpose media?
It supports the growth of most gram-positive and gram-negative bacteria
What is horse blood agar made from?
Proteins sources
Sodium chloride
5% blood
What is enriched media?
Media fortified with yeast extracts or protein infusions, useful in growing fastidious organisms
What are enriched medias fortified with?
Yeast extracts
OR
Protein infusions
Give an example of an enriched media.
Chocolate agar
What is present in chocolate agar?
Red blood cells that have been lysed
Name two fastidious organisms that require chocolate agar.
Neisseria meningitis
Haemophilus influenzae
What are selective medias?
Selective medias encourage the growth of one organism whilst suppressing the growth of another
Give an example of a selective media.
MacConkey agar
What does MacConkey agar contain that act as selective agents?
Bile salts and crystal violet
What is MacConkey selective for?
Gram-negative rods
What are differential medias?
They differentiate target organisms from a mixed culture
Give an example of a differential media.
MacConkey agar
What are the differential agents in MacConkey agar?
Peptone
Lactose
Neutral red dye
Give an example of a selective differential media.
Mannitol salt agar
What is the selective agent in mannitol salt agar?
High salt content
What is the differential agent in Mannitol salt agar?
Mannitol and the indicator phenol red
What is needed for anaerobic growth to be achieved?
An anaerobic jar or cabinet with all the oxygen removed
