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Medical Microbiology > Written Lab Final Questions > Flashcards

Written Lab Final Questions Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

what are three important procedures using aseptic technique

A

transfer with loop
transfer liquid with pipet
isolating pure culture

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2
Q

process of preparing a streak plate

A 
protect from contamination
mark bottom of dish
streak with loop of bacteria
flame loop and cool
repeat for 3 sections
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3
Q

what is microbiology the study of?

A

organisms too small to be seen with the naked eye

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4
Q

the modern compound light microscope consists of?

A

two lens systems

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5
Q

what is the objective lens?

A

lens closest to the material on the slide

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6
Q

what is the ocular lens?

A

eyepiece that magnifies the image formed by objective lens

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7
Q

how do you find the total magnification?

A

multiplying eyepiece lens by objective magnification

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8
Q

what are the factors that limit resolution of a lens?

A

angle

wavelength of light entering scope

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9
Q

what cannot be seen under a light microscope?

A

viruses

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10
Q

to observe bacteria in a stained or wet mount it is necessary….

A

to use an oil immersion lens

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11
Q

what is the most common way to stain organisms

A

gram stain

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12
Q

what is one of the first procedures employed in identifying organisms?

A

gram stain

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13
Q

what does gram stain do?

A

reveals:
morphology
arrangement
information of cell wall

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14
Q

what do gram positive cell walls have?

A

thick peptidogylcan

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15
Q

what is the procedure for gram stain?

A
  1. put water on slide
  2. place organism on slide
  3. heat fix
  4. flood slide with crystal violet
  5. rinse with water
  6. iodine
  7. water
  8. ethanol
  9. water
  10. safranin
  11. water
  12. blot
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16
Q

why is acid fast useful?

A

it helps identify bacteria with waxy lipid cell wall

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17
Q

what is the function of a capsule?

A

protect bacterium from WBC engulfment

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18
Q

what is the function of the endospore?

A

protects organisms from heat, chemicals and starvation

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19
Q

what is a direct count?

A

suspension of bacteria is placed on slide that has been ruled into squares

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20
Q

what are the methods of enumerating bacteria?

A

plate count
direct count
turbiditic method

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21
Q

what is an example of an obligate aerobe

A

micrococus luteus

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22
Q

what is an example of an obligate anaerobe?

A

clostridium

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23
Q

what is an example of a facultative anaerobe?

A

e. coli

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24
Q

what are some physical methods used to mill microorganisms?

A

heat and uv light

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25
Q

what effect does cold temps have on microbes

A

inhibit but do not kill

26
Q

what microorganisms produce heat resistant endospores

A

bacillus and clostridium

27
Q

what is an example of irreversible denaturation?

A

dehydrating microorganisms

28
Q

what is the typical sterilization time and temps?

A

2 hours at 165 for dry heat

15 at 121 for moist heat

29
Q

how does uv light kill microorganisms?

A

dna mutations

30
Q

what is the actual mechanism of mutation?

A

formation of thymine dimers

31
Q

what are semi synthetic antibiotics?

A

chemically modifying naturally made antibiotics

32
Q

what are synthetic antibiotics

A

completely synthesized in lab

33
Q

what is the kirby bauer test?

A

test potency of antibiotics and drugs

34
Q

how is susceptibility to a particular antibiotic determined?

A

measuring diameter of the zone of inhibition

35
Q

what shows a positive coagulase test?

A

if cells clump together

36
Q

what are the benefits of normal biota?

A
  • prevent harmful organisms from colonizing the skin

- produce enzymes that inhibit nonresident organisms

37
Q

is staphylococcus epidermidis coagulase positive or negative?

A

negative

38
Q

is staphylococcus epiddermidis mannitol positive or negative?

A

negative

39
Q

what is the outcome of s. aureus coagulase/mannitol

A

positive

40
Q

what are some tests used to identify aureus over epidermidis?

A

blood agar plate, coagulate or mannitol

41
Q

what is s. aureus on a blood agar plate?

A

beta hemolytic

42
Q

what is epidermidis on a blood agar plate?

A

gamma or alpha

43
Q

what does a mannitol salt plate do?

A

contains phenol red ph indicator that turns yellow if mannitol is fermented

44
Q

what does streptococci produce?

A

hemolysins

45
Q

what do hemolysins do

A

act on red blood cells

46
Q

what test would you use to measure differences in the organisms ability to ferment different sugars, the presence of various enzymes and physical characteristics such as motility?

A

biochemical tests

47
Q

what is a macconkey agar plate?

A

selective/differential medium

48
Q

what color is lactose fermenting organisms on macconkey agar

A

bright pink

49
Q

what color is non lactose fermenting on macconkey agar?

A

cream

50
Q

what is a XLD plate?

A

selective/differential medium

51
Q

on an XLD plate, what color are lactose, sucrose and xylose fermentation?

A

yellow

52
Q

what color are non fermenting colonies on an XLD

A

red

53
Q

what is indole

A

product from cleaving amino acid tryptophan

54
Q

what is the ELISA test used for?

A

identification of plant, animal, and human viruses

55
Q

what are the two primary causes of water pollution?

A

dumping of sewage

fecal pollution of animals and humans

56
Q

what are the two microbiological methods commonly used to determine if a given water sample is polluted?

A

total number of microorganisms present in the water

indicator organisms

57
Q

what indicator organisms are most commonly used

A

coliform

58
Q

what are the two most important methods applied to detect coliform organisms

A

multiple tube fermentation

membrane filter technique

59
Q

what are the three tests of multiple tube fermentation

A

presumptive
confirmed
completed

60
Q

what is the most probable number test and why is it useful?

A

counting bacteria that reluctantly form colonies but grow readily in liquid mediu

61
Q

what is the confirmed test?

A

confirms presence of coliforms

62
Q

what are advantages of the membrane filter technique over the multiple tube fermentation

A

better reproducibility of results
greater sensitivity
shorter time

Medical Microbiology (10 decks)

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