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Micro 3010 > Unit 10 - Diagnosis of Infections > Flashcards

Unit 10 - Diagnosis of Infections Flashcards

1
Q

List some non-culture based methods

A
  • Microscopy (staining techniques)
  • Immunodetection
  • Molecular diagnostics
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2
Q

What are culture based methods

A

where we grow organisms in the lab

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3
Q

What are the goals of a clinical microbiology laboratory?

A
  • Identification of the microorganism in the patient specimen involved in the disease process
  • Detection of microorganisms or their products in specimens collected from the patient
  • Detection of the patient’s immune response to infection
  • Provide antimicrobial susceptibility of the isolated microorganism
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4
Q

Identification of microorganisms by _____ and ______

A

isolation and culture

*This determines presence/absence or number of microorganisms and susceptibility

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5
Q

Identification of a specific microbial gene or product helps determine ?

A

Susceptibility? Presence of a resistance gene

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6
Q

Detection of specific antibodies to a pathogen determines ?

A
  • Pathogens that cannot be cultivated
  • High risk group pathogens
  • Retrospective diagnosis
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7
Q

When processing specimens, we need to determine if the site is ..?

A

sterile or a site with commensal flora present

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8
Q

Specimen processing can either be ______ or ______

A

culture based
or
non-culture based

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9
Q

Describe culture based specimen processing

A
  • > 18 hours
  • slow growing organisms
  • blood culture
  • culturable
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10
Q

Describe non-culture methods

A

Advantages:

  • fast
  • less labor intensive
  • suitable for organisms that cannot be cultured in the lab
  • Microscopy
  • Immunodiagnostics
  • Molecular diagnostics
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11
Q

What are the two branches of microscopy?

A
  • light microscopy

- electron microscopy

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12
Q

Bright field microscopy uses a ___ ____

A

gram stain

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13
Q

A gram stain shows you ______

A

morphology

as well as gram positive or gram negative

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14
Q

Briefly describe the gram stain process

A
  • Stain cells with crystal violet (purple)
  • Add iodine which makes the stain stick
  • Wash with ethanol
  • Crystal violet will be lost only from cells that have thin peptidoglycan (gram negative)
  • Stain with safranin (pink)
Purple = gram positive
Pink = gram negative
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15
Q

Describe acid fast light microscopy

A

mycolic acid cells are easy to stain but very hard to remove the stain ?

you determine which ones are acid fast by green vs pink

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16
Q

Light microscopy can also show ______

A

macromolecules

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17
Q

______ staining is another form of light microscopy

A

Fluorescent

18
Q

Describe fluorescent staining

A
  • naturally fluorescent

- stained with fluorescent dyes

19
Q

Describe electron microscopy

A
  • Resolution = 0.1 - 1.0 nm
  • Electron beam instead of light
  • Magnets instead of lenses
  • Thin specimen
  • SEM vs TEM
  • Viruses
  • Not routinely used in clinical labs
20
Q

Describe immunodetection

A
  • A lot more rapid than culturing
  • Specific Ab coated onto latex bead -> visible clumping
  • Can cause false-positives
21
Q

Common causes of bacterial meningitis?

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Neisseria meningiditis in CSF
22
Q

How do we quantify Ag/Ab?

A

ELISA

enzyme-linked immunosorbent assay

23
Q

Describe ELISA for an antigen

A
  • Bind antibody to solid phase
  • WASH
  • Add unknown antigen
  • WASH
  • Detect bound antigen with labeled 2nd antibody
  • WASH
  • Measure label
24
Q

Describe ELISA for an antibody

A
  • Bind antigen to solid phase
  • WASH
  • Add unknown antibody
  • WASH
  • Detect bound antibody with labeled anti-antibody
  • WASH
  • Measure label
25
Q

Describe how monoclonal antibodies are produced using tumor cells injected into a mouse

A

1) Tumor cells are injected into a mouse to stimulate production of B cells, which produce different types of antitumor antibodies
2) Immortalized myeloma cells are collected
3) The B cells are fused with the myeloma cells to produce immortalized, antibody-producing hybrid cells
4) The hybrid cell that produced the needed antibody is selected and cloned to produce unlimited quantities of a monoclonal antibody

26
Q

What 2 types of methods are available for detection of specific genes?

A

1) probe-based methods
- labelled, single-stranded nucleic acid fragment to hybridize with the target DNA

2) amplification-based methods

27
Q

Describe probe-based methods

A
  • Hydrogen bond formation between bases
  • Need a probe that is long enough to ensure specificity, but can’t be too long because it will bind to itself
  • Probe is fluorescently labelled, if you see it, it is positive

ex. HCV RNA

28
Q

Describe amplification-based methods

A

PCR can be used to amplify a specific DNA sequence to produce millions of copies within a few hours

29
Q

Describe culture based methods

A
  • Solid and liquid media (isolation, solid media) ?? wtf kumar
  • Selective
  • Differential
  • Antimicrobial susceptibility
30
Q

Describe selective media

A
  • selective against different pathogens
  • allows growth of certain bacteria

ex. Mannitol salt agar
- Allows growth of salt-loving bacteria (gram positive)
- Inhibits growth of gram negative

31
Q

Describe differential media

A

-allows growth of both types of pathogens, but allows you to distinguish them (usually by color)

32
Q

What 3 types of hemolysis are possible on blood agar?

A

alpha hemolysis
beta hemolysis
gamma hemolysis

33
Q

alpha hemolysis

A

partial hemolysis of red blood cells

34
Q

beta hemolysis

A

complete hemolysis of red blood cells

35
Q

gamma hemolysis

A

no hemolysis of red blood cells

36
Q

Obligate intracellular organisms produce a _____ effect

A

cytopathic

  • labor intensive and slow
  • immunodetection, molecular methods
37
Q

see slide 21

A

alright

38
Q

Successful clinical diagnosis of infection depends on?

A

proper specimen collection, transport, and processing

39
Q

Diagnosis is based on?

A

detecting microorganisms, their products, or patient’s immune response to the presence of infectious agent

40
Q

Interpretation of culture results depends upon the source of the specimen: ________ vs _________

A

sterile sites vs normal flora

Micro 3010 (20 decks)

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