Micro Lab Practical 3

  1. PEA - Selective, Differential or Both?
  2. Inhibiting agent in PEA & what it inhibits.
    • Phenyl Ethyl Alcohol;
    • gram (-)
  3. Name 2 species that grow on PEA.
    • S. aureus
    • S. pyogenes
  4. What microbes grow best on PEA Agar?
    gram (+)
  5. What kind of test is 6.5% Salt Broth?
  6. What does a Salt Broth test separate?
    E. fecalis & S. bovis
  7. HE Agar - Selective, Differential, or Both?
  8. What makes HE Agar selective? Differential?
    • Selective = bile salts inhibit gram (-)
    • Differential = iron turns black
  9. What are the sugars in HE Agar?
    lactose, sucrose, salacin
  10. What does HEA stand for?
    Hektoen Enteric Agar
  11. Name 2 pathogens in which HEA is used to isolate and ID.
    • Salmonella ¬†(produces H2S)
    • Shigella (does not produce H2S)
  12. If the TSI test shows a black butt, what does that mean and what test should you do next?
    It means it's Salmonella or Proteus. Do a urease test.
  13. What microbe is alpha hemolytic?
    S. pneumoniae
  14. Is an alpha hemolytic microbe bacitracin resistant or sensitive?
  15. In a Hemolysis test, what does a complete zone of clearing indicate?
    Beta hemolysis (complete hemolysis)
  16. What microbes are beta hemolytic?
    Group A Strep (S. pyogenes)
  17. Are beta hemolytic microbes sensitive or resistant to bacitracin?
  18. The oxidase test detects the presence of what enzyme?
    cytochrome oxidase
  19. Name one gram (-) diplococcus pathogen that is positive for cytochrome oxidase.
  20. What diseases does Neisseria cause?
    gonnorrhea; menengitis
  21. What is the Kirby Bauer test used to determine?
    Sensitivity and resistance to antibiotics
  22. What does a large ZOC in a Kirby Bauer test indicate?
    sensitivity to antibiotics
  23. What kind of test is a Bile Esculin test?
    gram (+) strep test
  24. Is Bile Esculin Selective, Differential, or Both?
  25. Esculin is a substance that is converted to what?
    glucose & esculetin
  26. What makes the Bile Esculin test selective?
    bile salts inhibit gram (+) EXCEPT Group D Strep
  27. What is the substrate in Bile Esculin Media?
    Esculin - can be digested to esculetin; in presence of iron will change color (black)
  28. Describe a positive Bile Esculin test.
    dark brown/black
  29. What is added to Bile Esculin media to give it a positive reaction?
  30. What group are positive for growth and esculin digestion?
    Group D Strep
  31. Name two species of gram (+) cocci in which Bile Esculin media is used to differentiate.
    E. fecalis; S. bovis
  32. What specific organism produces dark, blue-black colonies with a metallic green sheen on EMB agar?
    E. coli
  33. Is E. coli coliform or non-coliform?
  34. EMB is frequently used in water testing labs to detect what?
    fecal pollution
  35. What is the substrate and what are the end products in a catalase test?
    • substrate = H2O2
    • end products = H2O & O2
  36. Which gram (+) cocci produces a (+) result for the catalase test? Which produces a (-) result?
    • Staph = POS
    • Strep = NEG
  37. What does the catalase test separate?
    Staph & Strep
  38. MAC - Selective, Differential or Both?
  39. What are the inhibiting agents in MAC?
    Bile salts & crystal violet
  40. What is the MAC media selective for?
    gram (-)
  41. If you get pink colonies on a MAC plate, what does that indicate?
    a coliform
  42. What group of microbes does the MAC media inhibit?
    gram (+)
  43. What color is a positive fermentation on a MAC plate? What does it mean?
    pink; ferments lactose and is an acid
  44. What microbes will grow on a MAC plate?
    • E. coli
    • Enterobacter cloacae
    • Klebsiella pneumoniae¬†

  45. Why did we use Serratia marcesens in the UV light experiment?
    It grows fast and is red
  46. What is the target of the UV light in killing microbes?
  47. What does the UV light experiment cause to form?
    thymine-thymine dimers
  48. Describe light repair.
    • An enzyme system that can repair minor DNA damage;
    • light repair photo reactivating enzyme absorbs light & clears the thymine dimer to reform twoadjacent ¬†thymine residue
  49. Coagulase is the enzyme that causes _______ to be converted to ________.
    fibrinogen; fibrin
  50. Describe a positive coagulase test.
    solid; clump; clot
  51. Which pathogen will produce a positive coagulase test?
    S. aureus
  52. What do we use instead of coagulase on our flow chart?
  53. What does MSA stand for?
    Manitol Salt Agar
  54. What specific group of microbes do we use MSA to ID?
  55. What is the indicator in MSA?
    Phenyl Red
  56. Name the potential pathogen that grows on MSA & is (+) for MSA.
    S. aureus
  57. Is MSA Selective, Differential, or Both?
  58. What makes MSA Selective?
    salt makes it selective for Staph
  59. Why is MSA hypertonic?
    7% salt which is greater than 1% isotonic
  60. Is Blood Agar Selective, Differential, or Both? Why?
    • Differential;
    • because of hemolysis
  61. What is added to blood agar to give it the red color?
    5% sheep blood
  62. What is the "A" disk?
  63. What is the "O" disk?
  64. Name one specific pathogen that gives a ZOC with an A disk on blood agar.
    S. pyogenes
  65. The ZOC around an A disk on blood agar indicates what?
    sensitivity to bacitracin
  66. What is the ZOC around the individual colonies on a blood agar plate?
    Beta hemolysis
Card Set
Micro Lab Practical 3
Lab 3