Lecture 2 - Laboratory Flashcards

1
Q

culture dependent

A

can grow organism in lab and study it

*Collect specimen > Isolate > Investigate / test > identify

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2
Q

culture independent

A

don’t need to grow it in lab to be able to identify and study it
*collect specimen> Investigate (test) > identify

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3
Q

what is important when it comes to specimens collection, why?

A

quality. Effects speed and accuracy of organism identification.
- contributes to better pt outcomes and avoids inappropriate treatment

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4
Q

what types of specimens can you collect?

A

throat swab, sputum, blood samples (sterile), wound swabs, urine, genital swabs, stool

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5
Q

what is an example of a sterile specimen, why?

A

blood sample.
arent in contact with bacteria, virus, fungus that is all over body – no chance for cross contamination.
– able to identify bacteria and such that isnt supposed to be in there

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6
Q

what are important details to label on specimen collection

A
  • sources (niches) –> can aid in identification (rash vs cat bite)
  • patient status can effect work up (healthy vs diabetic)
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7
Q

culture

A

a population of bacteria grown in defined medium and defined conditions in a laboratory

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8
Q

pure culture

A

growth of a single known species - what we want

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9
Q

mixed culture

A

holds two or more species (starting point)

-need to separate normal flora from causative agent

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10
Q

contaminated culture

A

includes unwanted microbes, usually introduced inappropriately
-living on pt but not actually the cause of infection

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11
Q

what is inoculation?

  • how is it completed
  • types?
A

Adding a small amount of sample (ex: urine, swab) to media to grow a culture
-only certain bacteria can grow on certain media

-Inoculated media is incubated to grow culture at 20 to 40 ºC, different atmospheres (aerobic, anaerobic)

Types of inoculation:
Streak plate (\/\/\)
Spread plate (L)

*goal is to isolate colonies

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12
Q

isolated colony

A

A population of cells on an agar plate that arise from division of a single cell
-dif species form colonies with distinct characteristics (morphology) like size and colour

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13
Q

what is colony morphology

A
  • differs between species - an be used to identify causative agent
  • media type also aids in identification (differential and selective or enriched)
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14
Q

differential media

A
  • Contain chemicals that allow distinction of different types of bacteria based on colony morphology (d/t specific trait like metabolism)
    ex) mackonkey agar - identify lactose fermentation or not
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15
Q

Selective Media

A
  • prevents growth of a specific group of microbes, while allowing growth of others
  • target general groups (gram + or gram - or staphylococcus)
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16
Q

enriched media

A

contains organic molecules to grow Fastidious Microbes

17
Q

what are fastidious microbes

A

microbes that have complex nutrient requirements Ex. vitamins, growth factors

  • many pathogens are fastidious and rely on their host for nutrients
    ex) hemophelus influenza that causes meningitis needs heme (iron) and vitamins
18
Q

what are biochemical tests?

A

identify bacteria based on the enzymes they produce

-test for metabolic enzymes by growing in different nutrient sources

19
Q

what are immunological tests?

A

use antibodies to detect specific antigens that are found on microbes

  • can be culture dependent or independent
  • ex) O-antigen test would identify V. cholerae O139, E. coli O157
20
Q

what is agglutination

A
  • Antibodies detect and bind specific surface antigens on microbes
  • Antibodies can bind multiple microbes, cause visible clumping, indicating a positive reaction
21
Q

what is the reasoning behind staining

A

bacterial cells are clear and require staining to be visible

22
Q

what are the types of stains?

A

Positive stain: stains the bacteria
Negative stain: stains the background
differential staining - distinguished btw bacterial toes (gram +/- stain, endospore stain)

23
Q

how is investigation for independent cultures different than dependant cultures?

A
  • important in obligate parasites (chlamydia, viruses)
  • tests specific for organism
  • immunological tests - detection of antigens
  • molecular tests like PCR, DNA sequencing
24
Q

explain PCR

A
  • amplifies small amount of dana with specific sequence
  • allows detection of causative agent even in mixed samples at low concentration
  • detection of TB, chlamydia
25
Q

How does PCR work in the presence of mixed samples

A

DNA primers bind to specific microbial DNA, an enzyme duplicated DNA by exponential application –> microbial DNA can now be detected

26
Q

what is DNA sequencing?

A

direct identification by sequencing all DNA in a sample and comparing to data base of known organism DNA