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Microbioloy > Lab Quiz 4 revised > Flashcards

Lab Quiz 4 revised Flashcards

(60 cards)

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1
Q

33: what media is used in skin culture

A

Mannitol salt agar plate

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2
Q

33: What ingredient makes skin media selective and how is it selective

A

contains 7% salt which allows only salt tolerant organisms to grow

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3
Q

33: what ingredient make skin media differential and how is it

A

mannitol sugar
organisms that ferment mannitol grow yellow agar
non fermenting organisms remains red agar

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4
Q

33: what tests are used to determine if colony is a staph species

A
  • gram + cocci
  • catalase +
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5
Q

33: what test are used to identify staph species isolated

A
  • mannitol fermentation
  • coagulate
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6
Q

33: what is the reaction of coagulase

A

coagulase enzyme metabolizes fibrinogen into a fibrin clot

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7
Q

33: appearance of coagulase result

A
  • liquid media: -
  • clot formed: +
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8
Q

33: what species of staph produces coagulase

A

staph aureus

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9
Q

33: phenol red fermentation test explained and results

A
  • sugar fermented, acids produced, ph decreases, phenol red changes from red to yellow
  • yellow: +
  • red: -
  • phenol red indicator
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10
Q

35: what media are used for the mouth culture

A
  • Mitis-salivating agar
  • chrom agar candida
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11
Q

35: purpose of MSB agar

A

only allows growth of strep species which are prevalent in the mouth

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12
Q

35: How is MSB selective

A

crystal violet and telluride inhibit gram + and gram - growth excerpt for streptococcus

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13
Q

35: How is MSB differential

A
  • contains tryptan blue and sucrose
  • strep species blue black in color
  • differences in colony appearance identify species
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14
Q

35: purpose of chrom agar candida

A

isolation of candida species from saliva

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15
Q

35: how is chrom agar selective

A

chloramphenicol inhibits all gram + and gram - bacterial which allows candida yeast to grow

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16
Q

35: how is chrom agar differential

A

chromagenic granules metabolized differently by different species and appear different colors on agar

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17
Q

35: what species is commonly isolated on chrom agar and what is the appearance

A
  • candida albicans
  • apple green
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18
Q

35: what strep species is responsible for dental carie’s

A

strep mutans

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19
Q

35: what is the appearance of the 4 major types of strep on MSB agar

A

strep mitis: small, blue
enterococcus: small, black
strep salivarius: large, blue, gumdrop
strep mutans: blue, glass or burnt sugar

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20
Q

35: appearance of yeast cells under microscope

A

rain droplet like colonies with green tint

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21
Q

36: what medias are used for urine culture

A
  • 5% sheep blood agar
  • MacConkey agar
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22
Q

36: purpose of 5% sheep blood agar

A
  • good rich media that is non selective
  • determine total bacterial count per ml of urine
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23
Q

36: purpose of Macconkey agar

A
  • determine gram - bacteria count per ml of urine which is used to determine UTIs
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24
Q

36: how is macconkey agar selective

A

crystal violet and bile salts inhibit gram + growth and allow only gram - growth

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25
36: how is macconkey agar differential
contains lactose. lactose fermenting organisms produce dark pink/ purple colonies while non lactose fermenting organisms appear colorless/ yellow on agar
26
36: calculation for bacteria per ml of urine
amount of colonies x 100
27
36: criteria for a UTI
>10,000 organisms/mL urine and pure culture
28
36: criteria for minor and major contamination
- minor: < 10,000 bacteria/ml - major: >10,000 bacteria/ml with multiple colony types
29
36: what does growth on macconkey agar mean
- there is gram - organisms in urine but this does not mean UTI unless it meets uti criteria
30
36: what are UTIs caused by
gram - rods
31
36: define cystitis
UTI confined to bladder
32
36: Define pyelonephritis
UTI spread to kidneys
33
37: medias used in intestinal culture
- Bile Esculin hydrolysis media - Macconkey agar - EMB agar
34
37: purpose of bike esculin hydrolysis test
detect enterococcus fecalis in sample
35
37: Reaction of + bike esculin test
- esculin fecalis present in media and hydrolyses esculin to esculetin and dextrose - esculetin combines with ferric citrate indicator and turns black
36
37: How is bile esculin media selective
sodium azide and bile inhibit gram + and gram - growth except for enterococcus faecalis
37
37: gram stain of enterococcus faecalis
gram + cocci
38
37: purpose of macconkey agar
isolation of lactose fermenting, non pathogenic, gram - rod
39
37: how is macconkey agar selective
crystal violet and bile salts inhibit gram + bacteria and allow only gram - bacteria to grow
40
37: how is macconkey agar differential
lactose fermenting organisms appear pink/ purple and non lactose fermenting organisms appear colorless/ yellow
41
37: what tests are done to identify gram - rod isolated
- citrate - Urease - SIM - EMB agar plate
42
37: how is EMB agar selective
eosin/methylene blue inhibit gram + bacteria and allow only gram - bacteria to grow
43
37: How is EMB agar differential
organisms can be differentiated based on colony appearance
44
37: what is the appearance of E. coli on EMB agar
green, metallic sheen
45
38: what test is for antimicrobial drug and antibiotics
kirby bauer test
46
38: what is the purpose of kirby bauer test
assess the effectiveness of different drugs and antibiotics against specific microorganisms
47
38: what are the standardized features of kirby bauer test
- Muller Hinton agar media - 1+ turbidity of broth culture - concentrations of agent - method of measurement of zones of inhibition - charts used for interpretation: SIR
48
38: what media is used for kirby bauer test
Muller Hinton agar
49
38: process of kirby bauer test
- agar plate swabbed with broth culture - antibiotic disks placed on agar plate - zones of inhibition measured after incubation
50
38: why is it also called disk diffusion assay
gradient of highest concentration near the disk to lowest concentration away from the disk as the agent diffuses outward
51
38: define zone of inhibition
- clear are of no bacterial growth surrounding disk - formed when agent destroys pathogen - the bigger the size the more effective
52
38: how are kirby bauer results reported
- Sensitive - Intermediate - Resistant
53
39: What 3 organisms were tested against the agents
- E. coli - Staph aureus - pseudomonas
54
39: how was the effectiveness of each agent determined
- disk diffusion assay - zones of inhibition measured
55
39: does gram stain influence effects of agents
gram + bacteria is much more susceptible to affects of antiseptics and disinfectants than gram - bacteria
56
39: difference between antiseptic and disinfectant
antiseptic is used in the body while disinfectants are used on surfaces
57
40: alcohol mechanisms of action
- disruption of plasma membrane - denaturation of proteins
58
40: why are aqueous solutions superior to pure alcohols
denaturation of proteins more effective in presence of water
59
40: is alcohol effective as antiseptic or disinfectant
- both because it can be used in both surfaces and people - kills bacteria and fungi but not endospores or non enveloped - quadrant with alcohol thumb had no bacterial growth
60
41: take home lessons of hand washing
- extremely important in eliminating transmission of pathogen - sanitizer is very effective - need to wash hands for long time with soap while scrubbing to be super effective

Microbioloy (7 decks)

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