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IBI Test 1 > B3.003 Prework 1 Culture Based Diagnostic Tests > Flashcards

B3.003 Prework 1 Culture Based Diagnostic Tests Flashcards

1
Q

Koch’s postulates

A
  1. microorganism present in every case of the infectious disease
  2. microorganism can be isolated in pure culture
  3. inoculation of pure culture into animals produces similar disease
  4. same species of microorganism recovered from diseased animal
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2
Q

difference between envelopes of gram - and + bacteria

A

gram +
-thick peptidoglycan layer
-variable capsule
-potential for pili and flagella within envelope
gram -
-thin peptidoglycan layer
-variable capsule
-cytoplasmic and outer membrane
-periplasmic space
-cytoplasmic membrane> periplasm> peptidoglycan > outer membrane > capsule
-potential for pili and flagella within envelope

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3
Q

what component of the gram - cell wall is responsible for shock

A

Lipopolysaccharide (LPS) endotoxin

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4
Q

gram stain technique

A
  1. heat fix
  2. crystal violet stains all cells purple
  3. iodine solution: mordant-complexes with CV
  4. ethanol-acetone: destain, gram + retain CV/iodine complex
  5. safranin: counterstain; stains all cells pink
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5
Q

mycobacteria gram stain results

A

gram positive
but lipids interfere with stain
use acid fast

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6
Q

spirochetes gram stain results

A

gram negative
too thin to resolve
use wright-giemsa stain

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7
Q

sputum specimen collection

A

lower respiratory tract infection

avoid saliva

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8
Q

urine specimen collection

A

urinary tract infection

minimize contact with normal flora

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9
Q

feces specimen collection

A

diarrhea
rapid transport
large number of cultures
no direct stains

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10
Q

tissue specimen collection

A

center and border of lesion

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11
Q

pus specimen collection

A

abscess
aspirate
avoid swab

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12
Q

blood culture specimen collection

A

bacteremia
avoid contamination
ensure enough volume is collected per draw, 2 draws per patient

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13
Q

swab specimen collection

A

upper respiratory tract infection
swab inflamed areas
avoid saliva STDs
not for anaerobes

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14
Q

where do natural bacterial populations exist

A

skin
respiratory tract (oral cavity, pharynx)
GI tract (primary large intestine)
urogenital tract

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15
Q

upper respiratory tract normal flora

A

staphylococcus
streptococcus
haemophilus
anaerobes

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16
Q

skin normal flora

A

staphylococcus
coryneform (diptheroids)
propionibacterium

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17
Q

GI tract normal flora

A 
anaerobe
enterococcus
enterobacteriaceae
-Escherichia coli
-klebsiella
streptococcus
lactobacillus
candida
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18
Q

genital tract normal flora

A

lactobacillus

streptococcus

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19
Q

what characteristic of a sputum sample would indicate contamination?

A

> 10 epithelial cells per field

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20
Q

what feature of a sputum sample would indicate purulent infection?

A

presence of PMNs (polymononuclear cells)

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21
Q

growth media options

A

solid- agar

liquid - broth

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22
Q

enriched growth media

A

contains nutrients to support growth of a wide variety of organisms
blood agar, chocolate agar

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23
Q

selective growth media

A

inhibit growth of certain groups of organisms

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24
Q

differential growth media

A

distinguish organisms based on growth characteristics

25
Q

obligate aerobe

A

requires oxygen for growth

26
Q

facultative anaerobe

A

will grow in aerobic and anaerobic conditions

27
Q

microaerophilic

A

grows best with low concentrations of oxygen

28
Q

obligate anaerobe

A

oxygen is toxic

29
Q

MacConkey Agar

A

selective: inhibits growth of gram + organisms
differential: distinguished between ability to ferment lactose

30
Q

viral culture

A

growth on mammalian cells
not all viruses grow in viral culture
replaced by molecular methods in most clinical labs

31
Q

fungal culture

A

specialized media

incubation at lower temperature

32
Q

mycobacterial culture

A

broth and solid media

33
Q

alpha-hemolysis

A

green, incomplete lysis around colony

34
Q

beta-hemolysis

A

clear zone around colony

35
Q

gamma-hemolysis

A

no hemolysis

36
Q

yellow pigment production

A

staphylococcus aureus

37
Q

red/pink pigment production

A

serratia marcescens

38
Q

blue green pigment production

A

pseudomonas aeruginosa

39
Q

projections in colony

A

candida albicans

40
Q

mucoid colony

A

klebsiella pneumoniae

41
Q

swarming in colony

A

proteus vulgaris

42
Q

catalase reaction

A

gas formation

43
Q

coagulase reaction

A

precipitate formation

44
Q

oxidase reaction

A

blue color

identifies pseudomonas, Neisseria, vibrio

45
Q

methods of antimicrobial susceptibility testing (AST)

A

genotypic: PCR based detection of the genes associated with drug resistance
phenotypic: tests ability of organisms to grow in the presence of drug

46
Q

susceptible

A

isolate is inhibited by achievable concentrations of the antimicrobial agent

47
Q

intermediate

A

response rate isolate may be lower than that for susceptible isolates

48
Q

resistant

A

isolates are not inhibited by achievable concentrations of antimicrobial agent

49
Q

limitations of AST

A

imprecise

does not take into effect host response, toxin production, biofilm formation

50
Q

mecA gene

A

associated with methicillin resistance in s. aureus

51
Q

vanA/B genes

A

associated with vancomycin resistance in enterococcus faecium

52
Q

blaKPC gene

A

associated with carbapenem resistance

53
Q

advantages of genotypic testing

A

fast
very specific
very sensitive

54
Q

limitations of genotypic testing

A

expensive

single target

55
Q

MIC

A

minimum inhibitory concentration

minimum concentration of a drug that will inhibit growth of the organism

56
Q

methods of phenotypic testing

A

agar dilution
broth microdilution
disk diffusion
strip

57
Q

microbroth dilution

A

broth + increasing concentration of antibiotic in microtube or 96 well plate
inoculate isolate into each well
semi quantitiative

58
Q

strip testing

A 
paper strip with increasing concentration of drug
inoculate plate with lawn of isolate
place strip in center of plate
read MIC at area of growth inhibition
quantitative
59
Q

disk diffusion test

A

paper disk w single concentration of antibiotic place on agar inoculated with testing bacteria
measurement of the zones of growth inhibition
does not give MIC

IBI Test 1 (15 decks)

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