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Clinical Pathology II > Microbiology > Flashcards

Microbiology Flashcards

1
Q

what is microbiology used for?

A

useful but expensive and time-consuming diagnostic tool
identifying organisms can determine treatment

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2
Q

what do facilities usually do with samples for microbiology diagostics?

A

some send out all samples and others will plate the organisms and only send out if there is growth

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3
Q

are most microbes pathogenic or non-pathogenic?

A

non-pathogenic and make up normal flora

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4
Q

can normal flora be opportunistic?

A

yes

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5
Q

microbes from smallest to largest

A

prions, viruses, bacteria

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6
Q

prions

A

proteinaceous infectious agents
abnormally folded proteins
causes transmissible spongiform encephalopathies
doesn’t trigger immune response

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7
Q

viruses

A

obligate intracellular organisms = have to go into a cell to live
DNA or RNA surrounded by a protein coat
requires a host to replicate

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8
Q

types of viruses

A

bacteriophage, adenovirus, human immunodeficiency virus

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9
Q

bacteriology

A

study of bacteria

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10
Q

bacteria

A

prokaryotes= DNA is free in the cytoplasm
reproduce by binary fission= cell division

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11
Q

life cycle of bacteria

A

lag phase: adjustment
log phase: exponential growth (division)
stationary phase: cells stop dividing, growth is limited
death phase: cell loss

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12
Q

mycology

A

study of fungi

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13
Q

fungi

A

eukaryotes: DNA in the nucleus, organelles in the cytoplasm and membrane
reproduce by binary fission: budding (fruiting body is the spore)

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14
Q

protozoa

A

unicellular eukaryotes
binary fission to reproduce

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15
Q

how are protozoa classified?

A

by locomotion
amoeboids: pseudopodia
ciliates: cilia
sporozoa: non-motile
flagellates: flagella

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16
Q

bacteria growth requirements

A

pH: 7
oxygen or no oxygen (depends on type)
growth requirement factors affect which media we choose

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17
Q

oxygen tension

A

concentration of oxygen at a specific pressure

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18
Q

mesophilic bacteria temperature requirements

A

moderate temperature
20-40 C

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19
Q

psychrophile bacteria temperature requirements

A

low temperature

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20
Q

thermophile bacteria temperature requirements

A

high temperature

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21
Q

fastidious bacteria growth requirements

A

complex nutritional needs

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22
Q

oxygen requirements

A

aerobes: require O2
anaerobes: require absence of O2 (will die or have inhibited growth in O2 presence)

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23
Q

facultative

A

describes a bacteria that can grow under a variety of conditions
can survive without O2 but may have inhibited growth or grow with O2

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24
Q

microaerophilic

A

describes bacteria that prefer reduced O2 tension
O2 tension means it needs O2 at a lower concentration than is present in the atmosphere with enhanced CO2

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25
Q

capnophilic

A

describes bacteria that requires high levels of CO2

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26
Q

culture media

A

can be solid or liquid form
supports the growth of microorganisms
come as plates, tubes, or slants
can be general purpose, enriched, selective, or differential

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27
Q

Mueller-Hinton (MH) media

A

general purpose
used for antibiotic sensitivity testing

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28
Q

Kirby-Bauer antibiotic susceptibility testing

A

culture and sensitivity test
agar diffusion test used to determine which antimicrobial to use
done by performing a pure culture on MH media
antibiotic impregnated discs placed on top of streaks

29
Q

Kirby-Bauer antibiotic susceptibility testing: plating process

A
  1. pure culture of bacteria in agar
  2. bacteria grown overnight (18-24 hours) with a thin wafer that contains a known amount of a relevant antibiotic
30
Q

reading a Kirby-Bauer test

A

if the bacteria are susceptible to the particular antibiotic from the disc, there will be an area of clear media where the bacteria are not able to grow around the disc: known as zone of inhibition

31
Q

what does a larger zone of inhibition indicate?

A

the bacteria are more sensitive to the antibiotic in that specific disc
considered to be sensitive to antibiotic

32
Q

what does a smaller zone of inhibition indicate?

A

the bacteria is considered to be resistant to that antibiotic

33
Q

what is the relationship between zone of inhibition and minimum inhibitory concentration (MIC)?

A

they are inversely related

34
Q

minimum inhibitory concentration (MIC)

A

the amount of an antibiotic required to prevent bacterial growth in an overnight culture
the MIC graph is used in conjunction with the zone of inhibition to determine the best antibiotic to use

35
Q

TSA agar plate

A

general purpose media
enriched media version: TSA with blood (blood agar plates: BAP)

36
Q

enriched blood agar plates (BAP)

A

promotes growth of even fastidious bacteria
grows a wide range of pathogens especially those that are difficult to grow

37
Q

differential blood agar plates (BAP)

A

detects and differentiates hemolytic bacteria particularly streptococcus spp.

38
Q

hemolysis results on BAP

A

beta= complete hemolysis (creates a clear zone around the bacteria)
alpha= partial hemolysis or “greening” of agar (greenish or slimy discoloration around colony)
gamma= no hemolysis

39
Q

thioglycolate broth

A

differential media in liquid form
grows most bacteria
used for anaerobes

40
Q

macconkey media

A

contains crystal violet
selective: selects for gram negative bacteria by suppressing growth of gram positive bacteria
differential: differentiates into groups by their use of lactose, differentiates gram negative since they release acid that turn the agar red

41
Q

Simmons citrate media

A

differential
uses citrate which makes it blue

42
Q

bile escalin agar

A

differential media
enterococci: brown/black

43
Q

brain-heart infusion broth

A

enriched media used for blood cultures and fastidious bacteria
differential: turns transparent if positive for strep

44
Q

inoculation

A

goal is to isolate bacteria of interest with aseptic method

45
Q

inoculation process

A
  1. streak the plate
  2. incubate (37 C for most pathogenic bacteria)
  3. evaluate
46
Q

what characteristics do we look at while evaluating an agar plate?

A

colony form, elevation, margin, texture, and pigmentation

47
Q

how often should agar plates be checked on throughout incubation?

A

check on the plates and report if growth is observed or not every 12-24 hours

48
Q

sub-culturing

A

determine the number of different colony morphologies present and sub-culture each one to a separate plate so there are pure cultures available for analysis

49
Q

streaking the agar plate

A

use 4 streaks in the 4 quadrants of the plate in order to get distinct isolated colonies of bacteria

50
Q

hyphae

A

fungal filaments that are branching
they grow towards food sources and release digestive enzymes that break food up into small molecules

51
Q

how do fungi reproduce?

A

via sexual and asexual spores
different fungi groups produce different spores
fungi can be differentiated on the basis of hyphae structure and spore presence

52
Q

types of asexual spores

A

sporangiospores and conidia
conidia are exposed to the external environment at maturity but sporangiospores are enclosed from the external environment at maturity

53
Q

example of a spore

A

molds which are dispersed in the wind
there is 1 type of sexual spore produced by molds

54
Q

yeasts

A

candida (vaginal) and Malassezia (ears)
reproduce by budding

55
Q

dermatophytes

A

cutaneous mycotic organisms

56
Q

which dermatophytes cause ringworm?

A

Microsporum spp. and Trichophyton spp.

57
Q

dermatophyte spores

A

conidia
types: macroconidia- large, multicellular conidium
microconidia- single cell, small conidium

58
Q

why do we usually ID dermatophytes?

A

for fungal skin infections

59
Q

which media is used for IDing dermatophytes?

A

Sabouraud media which has antifungal and antibacterial agents to retard contaminant growth

60
Q

how can we tell if a DTM or Fungassay plate test is positive?

A

dermatophytes release alkaline metabolites which change pH indicator red so the media turns red if it is positive

61
Q

how can dermatophytes be viewed under the microscope?

A

in KOH on a slide with a cover slip
use clear tape and Lactophenol blue stain
evaluate on 10x-40x

62
Q

what are we looking for when viewing dermatophytes under the microscope?

A

look for hyphae and then macroconidia
may take up to 10 minutes to appear

63
Q

when performing a DTM test what type of fur do we try to pluck?

A

fur that appears to be damaged or crusting
use Mackenzie toothbrush method: using a toothbrush to brush along the damaged fur to collect a sample

64
Q

is using a Woods lamp reliable for ringworm?

A

no, it gives ambiguous results depending on the growth stage

65
Q

histoplasma

A

found worldwide
transmission: humid nitrogenous soil (especially increased bird/bat droppings), inhaled spores

66
Q

histoplasma CS

A

non-specific signs
usually see mild fever, depression, anorexia, weight loss
dogs can have respiratory/GI signs

67
Q

blastomycosis

A

“Chicago dz”
soil fungus
seen in warm moist environments
dogs are most susceptible
causes pulmonary disease, skin lesions, eye infections that could to blindness

68
Q

blastomycosis treatment

A

long term antifungal treatment
usually lasts up to 6 months

Clinical Pathology II (15 decks)

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