Exercise 16 - Basic Microbiology Media Flashcards
Selective media
Contains 1 or more agents that inhibit the growth (select against) certain bacteria; therefore encourages (selects for) others
Salt agar - TSA + 10% NaCL, Mannitol salt agar - MSA, MacConkey Agar - MAC
General purpose media
Designed to grow a broad spectrum of bacteria
Trypticase Soy Agar - TSA
Differential media
Designed to display visible difference amongst bacteria
Ex. Can they ferment or not, can they perform hemolysis or not
Mannitol salt agar - MSA, MacConkey Agar - MAC, Blood Agar - BA
Enrichment media
Contain ingredients (vitamins, proteins) that certain fastidious require for growth
Blood Agar - BA
Fastidious
Picky eater
Salt agar - TSA + 10% NaCL:
Types of media
Selective or differential agents
Selects for (+) , against (-)
Selective
S: 10% NaCL
+ Halophile or Halotolerant
- NonHalophile or NonHalotolerant
Trypticase Soy Agar - TSA:
Types of media
General purpose
Mannitol Salt Agar - MSA:
Types of media
Selective or differential agents
Selects for (+) and against (-)
Differential outcome
Selective and differential
S: 7.5% NaCL
D: Mannitol (sugar) and Phenol Red
+ Halophile or Halotolerant
- NonHalophile or NonHalotolerant
Fermentation of Mannitol
+ yellow agar
- red agar (NC)
MacConkey Agar - MAC:
Types of media
Selective or differential agents
Selects for (+) and against (-)
Differential outcome
Selective and differential
S: Bile Salts
D: Lactose and Neutral Red
+ Gram Negative Enterics
- Gram +
Fermentation of Lactose
+ red/pink colony
- white/opaque colony
Blood Agar - BA:
Types of media
Selective or differential agents
Differential outcome
Differential and enrichment
D: Blood (hemoglobin)
Beta hemolysis (clear)(has alpha toxin) Alpha hemolysis (green) Gamma hemolysis (NC)
MAC:
Differential agents:
Neutral red
If bacteria ferment Lactose, red/pink colonies (+)
MSA:
Differential agents:
Phenol red
If bacteria ferment Mannitol, decreases pH; acids produced
Agar turns from red to yellow (acid)
Three hemolysis patterns that can be observed in blood agar
Beta hemolysis “most” - agar will go from red to clear
Alpha (partial) - agar will go from red to green
Gamma hemolysis - (none) no color
What is the reaction of staphylococcus aureus in 7.5% mannitol salt agar? And why?
Turns agar yellow
Because it is a Halophile that ferments mannitol
What is the reaction of E. Coli in MAC? And why?
The E. Coli turns red/pink
Because it is a gram negative bacteria that ferments lactose
What is the reaction of staphylococcus aureus in blood agar, and why?
Turns the agar from red to clear
Because it has alpha toxin, making it beta hemolysis
What is the general shape of staphylococcus aureus and staphylococcus epidermis
Round (coccus)
What is the general shape of E. Coli and salmonella entorica
Rods (bacillus)
