Microbiology Review Questions #1

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Microbiology Review Questions #1
2010-12-30 15:38:15

Practical review questions for Neisseriaceae,Streptococcaceae, Antimicrobial susceptibility, Micrococcaceae, Gram positive Rods,
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  1. This direct smear is from a urethral discharge on a male; how would you report it out?
    Many PMNs and gram negative dipplococci

  2. This direct smear is from a urethral discharge on a male. What is the likely organism?
    Neisseria gonorrhoeae

  3. This chocolate plate was incubate in carbon dioxide. What is the term used for organisms that need increased carbon dioxide to grow?
  4. What is the selective plate that can be used for isolation of Neisseria gonorrhoeae & Neisseria meningitidis?
    Modified Thayer Martin or Martin Lewis agar
  5. What would be the expected oxidase test result if the organism is a Neisseria or Moraxella?
    Oxidase +

  6. Is it more likely Moraxella catarrhalis or Neisseria gonorrhoeae is growing on this plate?
    Moraxella since it grows better on blood agar. Neisseria gonorrhoeae does not grow or grows poorly on blood
  7. What is the term for Moraxella catarrhalis' nonfermentation of sugars?
  8. What tests are positive for Moraxella catarrhalis?
    • DNase +
    • butyrate esterase +
    • oxidase +
    • catalase +
  9. Would you do a Kirby-Bauer susceptibility test or a beta lactamase for Moraxella catarrhalis?
    beta lactamase

  10. From the results of these CTA sugars, what organism is this likely to be?
    Neisseria meningitidis
  11. What is the term used for the presence of Neisseria meningitidis in the blood stream?
  12. What would be the appearance of the CTA sugar tubes if the caps had been loose and the tubes were in increased carbon dioxide?
    They would all appear positive since the carbon dioxide would combine with water to form carbonic acid and that would turn the phenol red to a yellow color
  13. What member of the Streptococcaceae family will give a positive for both bile esculin agar and 6.5% NaCl broth?
    Group D Enterococci (Enterococcus faecalis, Enterococcus faecium, Enterococcus durans)
  14. What other test is positive for Enterococcus spp. other than Bile esculin and 6.5% NaCl?
  15. What organism(s) would give a positive Bile esculin and negative 6.5% NaCl broth?
    Group D streptococci (Streptococcus bovis, Streptococcus equinus)
  16. What members of the Streptococcaceae family will give a positive PYR test?
    Group D Enterococci and Streptococcus pyogenes (Group A)
  17. What organisms would give a positive esculin and positive PYR?
    Group D Enterococci
  18. What organisms would give a positive esculin and a negative PYR?
    Group D Streptococci

  19. What is the name of this test?
    Camp Test
  20. What organism produces this definitive arrow when close to Staphylococcus aureus (ie. Camp +) ?
    Group B streptococci (Streptococcus agalactiae)
  21. What would be the expected results for Streptococcus agalactiae for PYR and Esculin?
    Negative for both
  22. What organism will give a positive hippurate test?
    Streptococcus agalactiae
  23. If we isolate Streptococcus agalactiae from a spinal fluid, what is the likely age of the patient?
  24. What would be the expected Bacitracin susceptibility for Streptococcus agalactiae?
  25. Describe the type of hemolysis seen with Streptococcus agalactiae.
    Beta hemolysis
  26. Which streptococci is susceptible to bacitracin?
    Group A streptococci (Streptococcus pyogenes)
  27. What Micrococcaceae family member is susceptible to bacitracin?
    • Micrococcus spp.
    • Note: Staphylococcus spp. are resistant.

  28. What type of hemolysis is present?
    Are these colonies more suggestive of Group A, Group B, or Streptococcus pneumoniae?
    Beta hemolysis, suggestive of group A streptococcus.
  29. What is the chemical compound found in the Optochin disk?
    Ethylhydrocuprein hydrochloride
  30. What other rapid test (other than optochin) can be done to identify Streptococcus pneumoniae?
    Bile solubility
  31. How do you detect penicillin resistance for Streptococcus pneumoniae?
    To determine penicillin resistance the oxacillin disk is read. (Oxacillin is the surrogate disc.)
  32. What should be the depth of the Mueller Hinton agar?
    Approx 4mm

  33. What organism is growing on this Kirby-Bauer susceptibility test?
    Pseudomonas aeruginosa
  34. Why is the depth of the Mueller Hinton agar important?
    If the agar is too thick, the zone sizes will be smaller. If it is too thin the zone sizes will be bigger.

  35. What are you reporting out with the "E-test"?
    MIC values
  36. What are advantages of the "E-test"?
    You can perform the test on media the organism is routinely grown on.
  37. If an organism produces beta-lactamase, what groups of drugs does it have resistance to?
    • penicillins
    • cephalosporins
  38. What organisms would you do a beta lactamase test for?
    • Neisseria gonorrhoeae
    • Moraxella catarrhalis
    • Haemophilus influenzae
  39. Which genus of the Micrococcaceae family is sensitive to bacitracin?
  40. What are the characteristics that put an organism in the Micrococcaceae family?
    • Gram positive cocci
    • Catalase +
  41. What would be the result for bacitracin sensitivity for Staphylococcus epidermidis?

  42. This is the catalase test. What is the reagent used for this test?
    3% hydrogen peroxide
  43. The catalase test is used to differentiate which gram-positive cocci?
    Staphylococci and micrococci, both positive, from streptococci, that are negative
  44. What is the problem with performing a catalase test on blood agar or accidentally picking up blood agar with the colony?
    Blood is also capable of breaking down hydrogen peroxide into water and oxygen (false positive)
  45. What is the most likely type of hemolysis seen with Staphylococcus aureus?
    Beta hemolysis
  46. What identification tests are positive for Staphylococcus aureus?
    • Catalase +
    • Coagulase +
  47. What is the result expected for novobiocin susceptibility for Staphylococcus saprophyticus?
  48. What patient population is more likely to have urinary tract infections due to Staphylococcus saprophyticus?
    Young sexually active females

  49. Which organisms would give this Gram stain morphology from a specimen?
    • Staphylocci
    • Micrococci

  50. How would you perform a tube coagulase test?
    • Place approximately 1/2 ml of rabbit plasma in a sterile tube, inoculate the plasma with the test organism and then incubate at 37oC for 4 hours
    • *Note: leaving it longer in the incubator could result in a false negative due to fibrolysis.

  51. Which organism(s) produce "sulfa granules" in the exudate from the infection?
    • Nocardia
    • Actinomyces
  52. If you gram stain the yellow flecks of "sulfa granules" what would be the gram stain reaction and morphology of the organism(s)?
    Gram positive rods that are long, filamentous and branching
  53. Between Nocardia and Actinomyces,
    which of the organisms is aerobic and which is anaerobic?
    • Nocardia is aerobic
    • Actinomyces is anaerobic

  54. The lower picture is a Gram stain and the top picture is a modified acid stain of the same organism. What branching gram positive rod is acid fast?
  55. What type of specimens might contain Nocardia?
    • subcutaneous abscesses
    • sputum
    • jaw infections

  56. What organism causes black lesion like these?
    Bacillus anthracis
  57. Is Bacillus anthracis beta hemolytic on blood agar?
  58. What is the Gram stain morphology of Bacillus anthracis?
    Gram positive rods with spores
  59. What is the lecithinase result on Egg Yolk agar for Bacillus anthracis?
  60. If you had a nonhemolytic colony on blood that was motile, could you rule out Bacillus anthracis?
    Yes since B.anthracis is nonmotile

  61. This is Tinsdale Agar that is used for what organism?
    Corynebacterium diphtheriae
  62. What other selective media can be used for Corynebacterium diphtheriae?
    • Loeffler's
    • Cystine tellurite
    • etc.
  63. What is the name of the test used to determine if Corynebacterium diphtheriae produces the toxin that causes the disease?
    Elek plate with a anti-toxin strip that reacts with the toxin. (Precipitation antigen/antibody test)
  64. What would be the appearance of the motility in a wet prep for Listeria monocytogenes?
    • Tumbling motility
    • *Notes: In motility media, it has an umbrella shape.
  65. What would be the CAMP test result for Listeria monocytogenes?
    Camp +
  66. This Gram-positive rod is faintly beta hemolytic on blood agar and may look like Group B streptococci; what is it?
    Listeria monocytogenes
  67. What type of food products may result in food poisoning due to Listeria monocytogenes?
    • Mushrooms
    • milk products
    • deli meats (cold cuts)
  68. How would you describe the smell of Haemophilus influenzae?
  69. What media would support the growth of Haemophilus influenzea?
    • chocolate agar
    • Haemophilus isolation agar

  70. Starting at the top left quadrant: X only
    Top right: V only
    Bottom right: XV combined
    Bottom left: Horse Blood agar

    What organism is this?
    H. parahaemolyticus
  71. What would be the expected growth reactions for Haemophilus influenzae?
    • Growth in the XV quadrant
    • no hemolysis on Horse Blood agar
  72. What other test would be positive for H.parainfluenzae & H.parahaemolyticus?
    ALA (Porphyrin) test
  73. What is the term used to describe colonies growing around other colonies that provide V factor?
  74. What organisms can provide V factor?
    • Staphylococcus aureus
    • Neisseria
    • Streptococcus pneumoniae
  75. What organisms will only grow on sheep blood agar if V factor is provided by another organism?
    Haemophilus spp.
  76. How is sheep blood different from horse or rabbit blood when growing Haemophilus spp. ?
    Sheep blood contains NADase that breaks down V factor

  77. If this was identified as "mercury drop" colonies on Bordet' Gengou, what organism is it likely to be?
    Bordetella pertussis
  78. What type of specimen is collected for Bordetella pertussis?

  79. The picture at the right is a heart at autopsy. The arrow is pointing to infected heart valves. What is the term used for this type of infection?
  80. The HACEK group all cause endocarditis. What organisms belong to the HACEK group?
    • Haemophilus aphrophilus
    • Actinobacillus actinomycetemcomitans
    • Cardiobacterium homins
    • Eikenella corrodens
    • Kingella spp.
  81. What are the common characteristics of the HACEK group?
    • Need CO2
    • important cause of endocarditis
    • normal flora of the oral cavity
  82. Which one of these organisms line up on Gram stain as rosette, stick-like forms?
    Cardiobacterium hominis
  83. If the organism is from a dog bite or a cat-licking a wound, what is the likely organism?
    Pasteurella multocida
  84. Does Pasteurella multocida grow on MacConkey?
  85. What is the Gram stain morphology of Pasteurella multocida?
    • Gram-negative coccobacilli
    • bipolar staining is common
  86. What are the catalase and oxidase reactions for Pasteurella multocida?
    • Catalase +
    • Oxidase + (usually)

  87. If this blood culture from an individual who ate unpasteurized goat cheese, what Brucella organism is it likely to be?
    Brucella melitensis
  88. If this blood culture from an individual who raised beefalos, what Brucella organism is it likely to be?
    Brucella abortus
  89. What is the name of the Brucella organism associated with pigs?
    Brucella suis
  90. What is the biosafety levels for positive cultures for Brucella?
    Biosafety Level III

  91. This is a culture on Selective Buffered Charcoal Yeast Extract agar. What organism is likely to be isolated?
    Legionella pneumophilia