Micro - Lab Final

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  1. Oxidative catabolism requires what to grow bacteria
  2. Fermentative catabolism uses what to grow bacteria?
    starch hydrolysis (either peptone or glucose)
  3. Fermentation of bacteria using peptone does what to the medium?
    • Turns OF-glucose medium green to blue
    • pH goes up (alkaline)
  4. Fermentation of bacteria using glucose
    • Turns OF-glucose medium green to yellow
    • pH goes down (acidic)
  5. How can organisms that don’t use starch grow on a starch agar plate?
    They use peptones
  6. MRVP broth (RED) is used to determine the energy source ??? in fermentation
    • organisms that produce large amounts of acid from glucose
    • Remains red = positive and pH below 4.4 (acidic)
    • Turns yellow = neutral and pH above 6.0 (alkaline)
  7. Citrate agar (GREEN) is used to determine the energy source ??? in fermentation
    • Citrate use
    • Bacteria with the enzyme citrate lyase can break down citrate to form pyruvate
    • Turns blue = positive for the use of citrate acid
  8. During prolonged periods (greater than 24-hours) what may happen to the bacteria in a fermentation tube?
    • Exhausts the carbohydrate supplied
    • Grows oxidatively on the peptone
    • Turns red because of ammonia production
  9. Image Upload 1
    obligate aerobes
  10. Image Upload 2
    facultative anaerobes
  11. Image Upload 3
    obligate anaerobes
  12. Image Upload 4
    aerotolerant anaerobes
  13. Image Upload 5
  14. chemical agents used on inanimate objects to lower the level of microbes on their surfaces?
  15. chemicals used on living tissue to decrease the number of microbes
  16. Refers to agents used to kill bacteria
  17. Agent causing temporary inhibition of growth
  18. Variables to consider in selecting an antimicrobial agent
    • pH
    • solubility
    • toxicity
    • organic material present
    • length of contact
  19. Explain Disk-Diffusion method
    • Petri plate with agar
    • Inoculate uniformly over entire surface
    • Impregnate with paper disks (ABX, mouthwash, etc.)
  20. What is the Minimum Inhibitory Concentration (MIC)?
    the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism
  21. Name bacteria that reside on the skin
    • propionibacterium
    • staphylococcus aureus
    • staphylococcus epidermidis
  22. Why is S. Aureus different than the other microbiota of the skin?
    produces coagulase (enzyme that clots is pathogenic)
  23. What allows bacteria of the skin to survive?
    • resist drying
    • acidic
    • salt tolerant
  24. What bacteria primarily exist at the back of the throat?
    • Staphylococcus
    • Streptococcus
    • Neisseria
    • Haemophilius
  25. Beta-hemolytic group A streptococci (GAS) is which type of strep?
    S. pyogenes
  26. The importance of S. Pyogenes?
    • Most pathogenic bacterium in the whole genus (strep throat to toxic shock to necrotizing fasciitis)
    • Causes most Strep infections
  27. Greenish color around colonies on blood agar, partial destruction of RBC's is what type?
    Alpha hemolysis

    • S. pneumoniae
    • S. veridians
  28. complete hemolysis of RBC's on blood agar, a clear zone around the colony is what type?
    Beta hemolytic

    S. pyogenes
  29. no hemolysis and no change in the blood agar around the colony is what type?
    Gamma hemolytic
  30. S. pneumoniae vs. S. pyogenes
    S. pneumoniae will turn green on blood agar where S. pyogenes will have a clear zone around colony

    • S. pneumoniae
    • Optochin sensitivity
    • Bile solubility – activates an enzyme that lyses the cell wall

    • S. pyogenes
    • Sensitive to bacitracin – no others are
  31. What is the purpose of the Enterotube?
    • Rapid identification
    • Large number of results from one inoculation
  32. a protein enzyme that enables the conversion of fibrinogen to fibrin
  33. What does it mean when coagulase causes clumping?
    positive result - used to distinguish between different types of staph
  34. a common enzyme found in nearly all living organisms exposed to oxygen
  35. What is the result if Catalase causes bubbles?
    • positive result
    • It catalyzes the decomposition of hydrogen peroxide
  36. What is the test that estimates the concentration of antibody in serum?
    agglutination titration
  37. Why is the agglutination (titer of antibodies) titration test done?
    • Used to determine whether a particular organism may be causing the patient’s symptoms
    • An increase in titer in successive days is most likely a positive result
  38. Simple dilution problem...
    • 1ml bacteria added to 9ml nutrient broth = 1:10 
    • take 1ml of that dilution add to 9ml = 1:100…10x10x10x10x10 = 1:100,000 
    • number of colonies on plate of 1:1000 dilution is 54, 
    • then the count is 54 x 1000 = 54,000 bacteria/ml in sample
Card Set
Micro - Lab Final
Micro - Lab Final
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