Microbiology Test 1

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  1. The optochin test distinguishes between which two bacterial groups?
    Alpha-hemolytic Streptococcus pneumoniae and alpha-hemolytic Streptococci.
  2. Out of the alpha-hemolytic Streptococci species, which one is normally inhibited by optochin?
    Streptococcus pneumoniae
  3. SXT stands for the Sulfamethoxazole-Trimethoprim sensitivity test. What is the name of the antibiotic in this test?
  4. In the Bacitran test (SXT), what are the two groups that are distinguished?
    Between group A beta-hemolytic streptococci and non group A beta-hemolytic streptococci.
  5. In the Bacitran test (SXT), which group of beta-hemolytic Streptococci are sensitive to bacitran and which group are resistant?
    Group A are sensitive to bacitran while most non-group A are resistant.
  6. For the PYR test, what color designates a positive?
    Cherry Red
  7. The PYR test is used to identify a presumptive positive for what?
    Group A Streptococci
  8. When using PYR to identify a presumptive positive for Group A Streptococci, which other species will come up positive for this test?
  9. What causes food poisoning in the body via Staphylococcus aureus?
  10. Mannitol Salt agar is selective for which organism?
  11. Staphylococci and Streptococci are which type of organism? (Gram + or -)
    Gram +
  12. Which test do you use if you want to distinguish between Staphylococci and Streptococci?
    Catalase Test
  13. Out of Staphylococci and Streptococci, which organism is catalase negative?
  14. Which Staphylococci ferments mannitol?
    Staphylococcus aureus
  15. What has been added to mannitol salt agar that inhibits bacteria other than S. aureus?
    7.5-10% NaCl
  16. Modified Thayer-Martin agar is selective for which bacterial species?
    Neisseria (N. gonorrhoeae and N. meningitidis)
  17. Neisseria is gram positive or gram negative?
    Gram negative
  18. What is the component in Modified Thay-Martin agar that kills all gram negatives except Neisseria?
  19. What is the component in Modified Thay-Martin agar that kills fungi?
  20. What is the component in Modified Thay-Martin agar that inhibits gram negatives which include the prevention of swarming Proteus?
  21. These organisms are formally called Nutritionally variant streptococci and require what for growth?
    Pyridoxal or vitamin B
  22. Nutritionally variant streptococci are and organism that only grow around the colonies of other microbes. What is this process called?
  23. This form of Staphylococcus is pleomorphic and is negative for coagulase.
    Staphylococcus lugdunensis
  24. Staphylococcus lugdunensis is often confused with S. aureus during testing. Staphylococcus lugdunensis is PYR what?
  25. What are the virulence factors of Staphylococcus aureus? (4 things)
    1. Clumping factor (clots proteins that surround organism)

    2. Leukocidines (kills WBCs)

    3. Protein A (bins Fc instead of Fab, causes inhibition of opsinization and phagocytosis)

    4. Superantigen (overactivates T cells)
  26. What is the cause of necrosis in MRSA?
    PVL (Panton-Valentine Leukocidin)
  27. What does Beta-lactamase test for resistance to?
  28. What is considered a positive and negative test result for Beta-lactamase?
    • Positive: Pink
    • Negative: No color
  29. MacConkey's agar is supportive for which organisms?
    Gram negative bacilli
  30. MacConkey's agar utilizes which type of fermentation?
  31. For the CAMP test, how do you want to incubate the media?
    In ambient air
  32. MacConkey's agar is selective, differential, or both?
    Both, it selects for gram negative bacilli while inhibiting the growth of gram positive with crystal violet and bile salts.
  33. Which group of Strep organisms produce the camp factor?
    Group B
  34. This gram negative organism ferments glucose, but not maltose, lactose, sucrose, or DNAse?
    Neiserria gonorrehoeae
  35. During the Sodium Hippurate procedure, hippuric acid is hydrolyzed by hippuricase to produce which two byproducts?
    Glycine and benzoic acid
  36. During the Sodium Hippurate procedure, what reagent is used to detect the end product glycine to produce a blue color if positive?
  37. During the Sodium Hippurate procedure, how long after incubation do you add the ninhydrin reagent?
    2 hours
  38. Vancomycin inhibits which gram type of organisms?
    Gram positive
  39. Which are the larger of the two organisms?

    Moraxella or Neisseria?
  40. What is the compound used in the oxidase test is oxidized by cytochrome c  in the presence  of oxygen to produce a purple color?  
  41. Which compound is used in the bile solubility test?
    Sodium desoxycholate
  42. Which Streptococcus is soluble in bile salts while other alpha hemolytic strep are not?
    S. pneumoniae
  43. Streptococcus Pneumoniae has a requirement for what type of an environment?
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Microbiology Test 1
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