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microbioloy > Lab Quiz 4 revised > Flashcards

Lab Quiz 4 revised Flashcards

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
Q

36: how is macconkey agar differential

A

contains lactose. lactose fermenting organisms produce dark pink/ purple colonies while non lactose fermenting organisms appear colorless/ yellow on agar

26
Q

36: calculation for bacteria per ml of urine

A

amount of colonies x 100

27
Q

36: criteria for a UTI

A

> 10,000 organisms/mL urine and pure culture

28
Q

36: criteria for minor and major contamination

A
  • minor: < 10,000 bacteria/ml
  • major: >10,000 bacteria/ml with multiple colony types
29
Q

36: what does growth on macconkey agar mean

A
  • there is gram - organisms in urine but this does not mean UTI unless it meets uti criteria
30
Q

36: what are UTIs caused by

A

gram - rods

31
Q

36: define cystitis

A

UTI confined to bladder

32
Q

36: Define pyelonephritis

A

UTI spread to kidneys

33
Q

37: medias used in intestinal culture

A
  • Bile Esculin hydrolysis media
  • Macconkey agar
  • EMB agar
34
Q

37: purpose of bike esculin hydrolysis test

A

detect enterococcus fecalis in sample

35
Q

37: Reaction of + bike esculin test

A
  • esculin fecalis present in media and hydrolyses esculin to esculetin and dextrose
  • esculetin combines with ferric citrate indicator and turns black
36
Q

37: How is bile esculin media selective

A

sodium azide and bile inhibit gram + and gram - growth except for enterococcus faecalis

37
Q

37: gram stain of enterococcus faecalis

A

gram + cocci

38
Q

37: purpose of macconkey agar

A

isolation of lactose fermenting, non pathogenic, gram - rod

39
Q

37: how is macconkey agar selective

A

crystal violet and bile salts inhibit gram + bacteria and allow only gram - bacteria to grow

40
Q

37: how is macconkey agar differential

A

lactose fermenting organisms appear pink/ purple and non lactose fermenting organisms appear colorless/ yellow

41
Q

37: what tests are done to identify gram - rod isolated

A
  • citrate
  • Urease
  • SIM
  • EMB agar plate
42
Q

37: how is EMB agar selective

A

eosin/methylene blue inhibit gram + bacteria and allow only gram - bacteria to grow

43
Q

37: How is EMB agar differential

A

organisms can be differentiated based on colony appearance

44
Q

37: what is the appearance of E. coli on EMB agar

A

green, metallic sheen

45
Q

38: what test is for antimicrobial drug and antibiotics

A

kirby bauer test

46
Q

38: what is the purpose of kirby bauer test

A

assess the effectiveness of different drugs and antibiotics against specific microorganisms

47
Q

38: what are the standardized features of kirby bauer test

A
  • 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
Q

38: what media is used for kirby bauer test

A

Muller Hinton agar

49
Q

38: process of kirby bauer test

A
  • agar plate swabbed with broth culture
  • antibiotic disks placed on agar plate
  • zones of inhibition measured after incubation
50
Q

38: why is it also called disk diffusion assay

A

gradient of highest concentration near the disk to lowest concentration away from the disk as the agent diffuses outward

51
Q

38: define zone of inhibition

A
  • clear are of no bacterial growth surrounding disk
  • formed when agent destroys pathogen
  • the bigger the size the more effective
52
Q

38: how are kirby bauer results reported

A
  • Sensitive
  • Intermediate
  • Resistant
53
Q

39: What 3 organisms were tested against the agents

A
  • E. coli
  • Staph aureus
  • pseudomonas
54
Q

39: how was the effectiveness of each agent determined

A
  • disk diffusion assay
  • zones of inhibition measured
55
Q

39: does gram stain influence effects of agents

A

gram + bacteria is much more susceptible to affects of antiseptics and disinfectants than gram - bacteria

56
Q

39: difference between antiseptic and disinfectant

A

antiseptic is used in the body while disinfectants are used on surfaces

57
Q

40: alcohol mechanisms of action

A
  • disruption of plasma membrane
  • denaturation of proteins
58
Q

40: why are aqueous solutions superior to pure alcohols

A

denaturation of proteins more effective in presence of water

59
Q

40: is alcohol effective as antiseptic or disinfectant

A
  • 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
Q

41: take home lessons of hand washing

A
  • 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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