TEST 1 Microbial Structure and Classification

Question 1

What is general purpose growth media?

Answer 1

Blood agar

Question 2

What is enriched growth media?

Answer 2

• Special Nutrients add so many bugs will grow
• Blood and Chocolate agars

Question 3

What is selective growth media?

Answer 3

• Contains toxic substances such as Pseudomonas isolation agar (PIA)
• Only certain bugs will grow.
• Thayer-Martin agar grows only Neisseria.

Question 4

What is Differential growth media?

Answer 4

• Different bugs grow with different patterns
• Blood agar: alpha, beta hemolysis
• MacConkeys agar

Question 5

What is an example Anaerobic growth media?

Answer 5

Thioglycollate broth

Question 6

Features of Blood Agar?

Answer 6

• Commonly used to differentiate species of Streptococci
  
  • Alpha: Viridian or pneumonia
  • Beta: pyogenes or agalactiae
  • Gamma: Enterococci or bovis
• Special Feature of Pseudomonas
  
  • Beta hemolytic
  • Greenish-metallic appearing colonies
  • Pigements: Pyoverdin and pyocyanin
• Staphylococcus aureus
  
  • Beta-hemolytic

Question 7

Features of Choclate Agar

Answer 7

• Variant of blood agar
• Contains red blood cells that are lysed via heating
• Contains NAD (factor V) and hemin (factor X)
  
  • NAD from inside RBCs
  • Media heated such that they are not destroyed.
• H. Influenza will grow
• Classic scenario:
  
  • Bacteria won’t grow on blood agar unless S. aureus is present.

Question 8

Thayer-Martin Agar

Answer 8

• Enriched and selective for Neisseria
• Neisseria often from sites with lots of other flora (throat, genitalia)
• Supplemented chocolate agar
• Vancomycin: kills most G+