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microbiology > lecture 6) clinical microbiology 2 > Flashcards

lecture 6) clinical microbiology 2 Flashcards

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Biology 101 flashcards
1
Q

why study the cause of infection?

A

prognosis
treatment
isolation
care

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2
Q

name 5 ways the cause of infection can be determined

A 
microscopy
molecular testing
biochemical tests
rapid test and immunoassays
culture
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3
Q

what type of microscopy is used to identify infections of bacteria, fungi and protozoa?

A

light

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4
Q

what type of microscopy is used to identify viral infections?

A

electron

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5
Q

what molecular test can you do to identify infections of bacteria, fungi, protozoa and viruses?

A

nucleic acid amplification, sequencing, fingerprinting etc

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6
Q

what biochemical tests can be used to identify bacterial and fungal infections?

A

identification and sensitivity

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7
Q

what rapid tests can be used to identify bacterial and fungal infections?

A

biochemical identification

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8
Q

what immunoassay tests can be used to identify bacterial, fungal, protozoa and viral infections?

A

ELISA
flow cytometry
complement fixation

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9
Q

how would you culture bacterial and fungal infections?

A

purify and amplify

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10
Q

how would you culture viral infections?

A

cytopathology

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11
Q

what are the 4 steps in historical workflow of determining the cause of infection?

A

1) stain based methodologies
2) microbial cultures
3) biochemical/antigenic techniques
4) antimicrobial susceptibility testing

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12
Q

what is the aim of stain based methodologies and what do they support?

A

classification of microscopic morphology

supports early diagnostic and therapeutic decisions

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13
Q

what does microbial culture involve in historical workflow?

A

propagtion of organism on agar/liquid medium

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14
Q

what do biochemical/antigenic techniques involve and what does this lead to?

A

metabolic and phenotypic analysis

leads to identification of organism

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15
Q

what does antimicrobial susceptibility testing lead to?

A

confirming or tailoring therapeutic agents

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16
Q

give 3 examples of stains for microscopy

A

gram stain
acid fast stain
periodic acid schiff (PAS)

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17
Q

what is acid fast stain also known as?

A

zahl-neeson stain

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18
Q

how is acid fast stain done and what does it test?

A

performed directly on sputum (saliva + mucus coughed up from resp tract), no need for culture, specific
performed on mycobacteria

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19
Q

what is PAS used for?

A

stains glycoproteins in fungi

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20
Q

what type of background is needed for PAS?

A

high background

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21
Q

what is a disadvantage of PAS?

A

not very clear as it reacts with other cells that contain glycoproteins

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22
Q

name a selective media used for microbial culture

A

mannitol salt agar that is used for isolation of staphylococci

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23
Q

what does a selective media do?

A

supports the growth of one group of organisms out of a highly variable sample eg faeces

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24
Q

name a differential media used for microbial culture

A

MacConkey agar for the recovery of enterobacteriaceae

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25
Q

what property of mannitol salt agar plates prevents many bacterial strains from growing?

A

7.5% sodium chloride

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26
Q

what species of bacteria thrive in mannitol salt agar plates?

A

staphylococcus

ferment mannitol and produce an acidic product

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27
Q

what is the colour change for a positive result on mannitol salt agar?

A

red to yellow

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28
Q

what dye is used on mannitol salt agar plates?

A

phenyl red

29
Q

what does differential media do?

A

supports the growth of many bacteria and then you can isolate certain ones

30
Q

what type property of bacteria would cause a positive result on MacConkey agar plates?

A

lactose fermenters

31
Q

what is the colour change for a positive result on MacConkey?

A

red to pink

32
Q

what dye is used for MacConkey plates?

A

neutral red

33
Q

why are tests that differentiate staphylococcus and streptococcus important?

A

because staph and strep are both gram positive bacteria that are found on the skin

34
Q

name 3 biochemical techniques that can be used after gram staining?

A

coagulase
beta galactosidase
catalase

35
Q

what does coagulase detect?

A

detects the presence of coagulase that causes plasma to clot

36
Q

what bacteria does coagulase differentiate?

A

staphylococcus aureus and epidermis

37
Q

what does beta galactosidase detect?

A

detects the presenc of an enzyme that cleaves lactose to form glucose and galactose

38
Q

what does beta galactosidase differentiate?

A

separates the enterics and identifies pseudonomads

39
Q

what does the biochemical test catalase detect?

A

catalse

converts hydrogen peroxide to water and oxygen

40
Q

what dose catalse differentiate between?

A

staphylococcus and streptococcus

41
Q

name 2 tests that differentiate between staphylococcus and streptococcus

A

catalase

mannitol salt agar plate

42
Q

what test is the first form of information?

A

gram staining

43
Q

what is used to carry out biochemical tests?

A

API strips (analytical profile index)

44
Q

how many biochemical tests does API test for?

A

20

45
Q

what does ELISA stand for?

A

enzyme linked immunoabsorbent assay

46
Q

why would indirect ELISA be used?

A

if you want to find out if an individual has been infected with a certain pathogen

47
Q

what are the steps involved in indirect ELISA?

A

take a serum sample from the individual
clone the antigen and stick it to the plastic wells
if they have antibodies for the antigens on the well they will stick to it and others wont
wash everything that doesnt stick away
indicator antibody linked to enzyme attached to any bound antibody
rinse well to get rid of anything bound to them
colourless substrate added
enzymes that are linked to the indicator antibody hydrolyse the substrate releasing a dye

48
Q

what results are positive and negative from indirect ELISA?

A

coloured wells are positive for the antibody

colourless wells are negative for th antibody

49
Q

what viruses can be detected using antibody sandwich ELISA?

A

orthohantavirus

measles virus

50
Q

explain the steps in antibody sandwich ELISA

A

antibody absorbed to the well
test antigen added
enzyme linked antibody specific to test antigen binds to another antigen forming a sandwich
enzyme substrate added
if positive there will be a colour change

51
Q

what type of infections do agglutination assays commonly test for?

A

viral infections

52
Q

what do agglutination assays use?

A

uses the patients immune system to tell us what we have got

53
Q

what beads are used in agglutination of red blood cells and what do they do/tell us?

A

latex beads coated with an antigen
latex beads coated with a protein belonging to the virus
if you are infected with that virus you probably have antibodies for the virus therefore the antibodies with bind to the antigens on the latex beads
agglutination of the antibodies to the antigens on the beads can be monitored in the blood sample

54
Q

what happens to red blood cells that arent agglutinated?

A

the will pellet at the bottom of the well

55
Q

explain how you would test for antimicrobial suscpetibility using an agar plate

A

put the antibiotic on the agar plate
dot the microbe around the agar plate
if there is mirobial growth = resistant to antibiotic
no microbial growth = susceptible to antibiotic

56
Q

what is an Etest strip and what is it used for?

A

graded concentration strip

used for antibiotic susceptibiliy testing

57
Q

name 5 techniques used in modern clinical microbiology

A

next generation sequencing of whole bacterial genomes
metagenomics and community profiling
multiplex PCR
mass spectrometry

58
Q

which is the best technique used in modern microbiology?

A

mass spectrometry

59
Q

what can also be measured in mass spectrometry?

A

PCR

60
Q

how is mass spectrometry used?

A

detects mass/charge ratio

fragment will be in a certain pattern

61
Q

describe NGS of bacterial genomes

A

currently culture dependent
species identification
becoming cheaper
gives a wealth of information

62
Q

what are some of the advantages of using multiplex PCR?

A

differentiates strains based on the bands you have
no need for culture
cheap and sensitive
no comparison standard

63
Q

what are some of the disadvantages of multiplex PCR?

A

need 1 set of primers specific for each organism
too laborious
prone to error in set up

64
Q

what is used as an alternative to multiplex PCR?

A

NAAT

PCR

65
Q

what is culturomics also known as?

A

metagenomics and community profiling

66
Q

give some examples of gram positive bacteria

A 
streptococcus
staphylococcus
mycobacteria 
listeria
bacillus
clostridium
67
Q

give some examples of common negative bacteria

A

neisseria
enteronacteriacae
bacteriodes
campylobacter

68
Q

mycobacteria are classed as being gram positives. what would make them qualify as being gram positive and gram negative?

A

1 phospholipid bilayer
1 peptiodglycan layer

no asymmetric membrane (gram positive)
mycolic acids serve as pseudophospholipid bilayer
retain gram stain

microbiology (17 decks)

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