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diagnostic microbiology Flashcards

1
Q

culture media

A

why we want to culture
what we want to culture
who (what might be bothering your patient, who will it affect?)

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2
Q

inoculation methods

A

streak
spread
pour

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3
Q

streaking a plate for isolated colonies

A

to isolate
most common

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4
Q

steps for streaking

A

do a streak with blood sample
put it through a flame to sterilize
streak away from it
sterilize
(diluting sample, as you do each streak it dilutes)

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5
Q

pour plates

A

bacteria grows inside agar
used for enumeration of bacteria
to isolate
not as common now, popular a while ago

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6
Q

steps for pour plate

A

blood sample in empty dish
media poured on top
mix

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7
Q

spread plates

A

to QUANTIFY, not just isolate

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8
Q

preservation of cultures

A

pure cultures of bacteria are stored:
freeze dried (lyophilized)
frozen at -80 degrees C

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9
Q

preservation of pure cultures

A

short term:
- medium fridge temp (4-10 degrees C)
long term:
- liquid nitrogen (-195 degrees C)
- freezers
-lyophilization (freeze-drying)

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10
Q

why would we want to keep a copy of a bacteria we isolated from a patient

A

in case someone gets similar symptoms in the future, you could see if it’s the same thing as the sample

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11
Q

why do we isolate a pure culture from a specimen

A

able to study if it has a mutation or if it’s becoming more variant

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12
Q

identification: colony morphology

A

single bacteria that grows and multiplies to make a million

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13
Q

identification: cellular morphology

A

look at single bacterial cell under microscope

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14
Q

identification: staining techniques

A

3 steps:
- make a smear
- fix dried smear by heat
- stain with desired dye

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15
Q

simple stain

A

single dye normally used
all organisms same colour
size, shape, number, arrangement, etc…

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16
Q

differential stain

A

two or more dyes
differences between microorganisms or parts of cells
acid fast, GRAM

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17
Q

THE GRAM STAIN (HANS CHRISTIAN GRAM)

A
  1. flood crystal violet
  2. flood Gram’s iodine
  3. decolourize with 95% ethanol (most important)
  4. counter stain with pink safranin
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18
Q

after gram stain, gram + is

A

purple

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19
Q

after gram stain, gram - is

A

pink

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20
Q

cell wall is the key…

A

essential for cell growth and division

shape of bacteria related to peptidoglycan layer (WHERE CRYSTAL-VIOLET IODINE BINDS)

gram negative peptidoglycan usually thinner than gram positive

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21
Q

gram negative cell envelope

A

thin peptidoglycan cell wall
SECOND wall is ENDOTOXIC

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22
Q

gram positive cell envelope

A

big peptidoglycan layer
no endotoxins because no second wall

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23
Q

other stains

A

endospore
- malachite green applied with heat to penetrate spores followed by counter, staining with safranin

capsule
- treat with copper sulfate before staining to visualize capsule as a
clear zone surroundings cells

flagella
- use of mordant to thicken flagella before staining to
visualize

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24
Q

fluorescence microscopy

A

dye fluorescences at specific wavelength
antibodies tagged with dyes are common (immunofluorescence microscopy)

25
Q

electron microscopy

A

electron beam (instead of light)
million times magnification possible (0.003um)
- TEM (stain with heavy metals)
- SEM (3-D image of cell surface)

26
Q

morphology helps to…

A

classify and identify (gram stain)

27
Q

gives clues to how they behave in the environment with…

A

capsules, endospores

28
Q

characteristics of bacteria

A

small (0.75-1.25um in diameter/ width)

higher surface area/ volume, which is responsible for…

  • higher metabolism
  • faster growth
  • replication rate (20 min)
29
Q

shapes and sizes of bacteria
(arranged in specific patterns): single cells

A

spiral and/or rod shaped

30
Q

shapes and sizes of bacteria
(arranged in specific patterns): diplococci

A

pairs, single plane

31
Q

shapes and sizes of bacteria
(arranged in specific patterns): chain

A

divide in one plane and remain attached

32
Q

shapes and sizes of bacteria
(arranged in specific patterns): tetrads

A

cocci dividing at right angle to first plane of division

33
Q

shapes and sizes of bacteria
(arranged in specific patterns): division in three planes

A

grapelike clusters

34
Q

shapes and sizes of bacteria
(arranged in specific patterns): cubical packet of 8 cells

A

sarcinae

35
Q

chemically defined

A

exact composition known

36
Q

chemically undefined

A

some components can’t be controlled (beef extract, blood)

37
Q

if solid (vs. liquid) growth

A

1.5% agar used

38
Q

enrichment media

A

increase # of specific media in sample by favoring growth of interested species

Laboratory media designed to illustrate the ability (or not) of a bacterial to ferment sugars such as lactose

39
Q

tissue culture media

A

for cultivating viruses, derived of plant or animal cells

40
Q

general media requirements

A

bacteria - requirements vary
yeasts - high sugar and lower pH
anaerobes - must remove oxygen

41
Q

selective media

A

enhance growth of one bacterial species or suppression of another

42
Q

differential media

A

differentiate bacteria based on their nutritional requirements and phenotypic characteristics

43
Q

selective/ differential media

A

very useful in clinical labs (eg. MacConkey agar)

44
Q

MacConkey - S/D media

A

bile salts, crystal violet inhibit gram + (thus allowing gram - organisms)
neutral red dye helps detect lactose fermentation (colonies aren’t red!!)

45
Q

with what do we grow bacteria? - salmonella typhimurium

A

gram negative: growth
lactose fermentation: NEGATIVE
colourless colonies

46
Q

with what do we grow bacteria? - escherichia coli

A

gram negative: growth
lactose fermentation: POSITIVE
pink colonies (PINK, NOT RED)

47
Q

temperature definition: psychrophiles

A

grows best at 15-20 degrees

48
Q

temperature definition: mesophiles

A

grows best at 25-40 degrees
(most human pathogens and bacteria belong here, except listeria which is a psychrotroph/psychrophile)

49
Q

thermophiles

A

grows best at 40-85 degrees

50
Q

oxygen requirements: obligate aerobes

A

need oxygen to survive

51
Q

oxygen requirements: obligate anaerobes

A

no oxygen to survive

52
Q

oxygen requirements: facultative aerobes

A

prefers oxygen, doesn’t need

53
Q

oxygen requirements: aerotolerant anaerobes

A

able to tolerate oxygen

54
Q

oxygen requirements: microaerophiles

A

need specific amount of oxygen

55
Q

pH and water requirements

A

optimal pH varies for each bacteria
intracellular pH 7.5
growth observed at pH of 4-9 (optimal 6-8)
water (light) can be important for certain microorganisms
osmotic pressure (hypertonic, hypotonic, isotonic)

56
Q

ELISA

A

enzyme-linked immunosorbent assay

57
Q

DIRECT ELISA

A

detect an ANTIGEN
(more colour = more antigen)
(ex. pregnancy test, steroid test)

58
Q

INDIRECT ELISA

A

detects ANTIBODIES
(more colour = more antibodies)
(ex. HIV, will see if you have antibodies for HIV)

flashcards (24 decks)

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