Infection tests

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  • Created by: hadar
  • Created on: 04-02-18 20:29
What is fever a sign of?
Inflammation- and can be a sign/symptoms of infection
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What are the symptoms of a temperature?
1) fever (burning up) 2) chills, sweats, night sweats 3) rigors
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What are the 2 reasons to carry out a diagnostic test?
1) improve outcome 2) provide epidemiological data
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What is in a full blood count?
1) Haemoglobin 2) White cell count
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What does haemoglobin show?
Not helpful for infection--> helpful to show anaemia of chronic disease and can be caused by infection
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What does white cell count show?
Raised in infection (but also in other conditions so has poor specificity)
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What would a full blood count show in bacterial infection?
1) raised WCC 2) normal/low lymphocytes 3) raised neutrophils
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What would a full blood count show in viral infection?
1) normal WCC 2) raised lymphocytes 3) normal neutrophils
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What are inflammatory markers and name 2
elements of the innate immune system 1) C-reactive protein
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What are raised inflammatory markers an indicator of?
Infection
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What investigations can help identify a severe sepsis and respiratory failure?
1) blood lactate 2) blood gases
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What methods of microbiology diagnosis?
1) culture 2) direct detection 3)immunological tests
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What does direct detection include?
Detection of whole organism, antigen or genomic material
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What does serology detect?
An antibody response
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What is the principle of culture?
Isolation of viable pathogen --> 1) identification 2) typing- organism relatedness 3) sensitivity testing- direct antimicrobial therapy
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What is time to positivity (TTP)?
12-24 hours in significant bacteraemia but may be longer or shorter depending on sepsis and species -- the time it takes for the detected of bacteria
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What is gram stain used for and what do results mean?
Chemical process that distinguishes between bacterial cell walls that retain crystal violet, and those that do not, when stained and washed with acetone.--> gram +ve= purple gram -ve= prink
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What is the basic principle of sensitivity testing?
Culture of micro-organism in the presence of antimicrobial agent Work out if the concentration of antimicrobial that will be available in the body is high enough to kill the micro-organism
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What is the zone of inhibition?
An area around the wafer where the bacteria have not grown enough to be visible
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What are sensitivity tests used for?
Inform decisions on targeted antimicrobial therapy
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What is empiric therapy?
Initial treatment given before any investigation tests done on the basis of clinical features and symptoms
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What are the uses and limitations of culture?
1)Establishes the presence of a micro-organism at a particular site Cultivable organisms only 2)Allows the use of empiric and targeted antimicrobial therapy 3)Provides epidemiological and typing information 4)Is usually slower than direct detection
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Give examples of direct detection
1) whole organisms- microscopy 2)component of organism- antigen/ nucleic acid (RNA/DNA)
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What are the uses and limitations of direct detection method?
1)shows presence of a micro-organism at a particular site-Cultivable and non-cultivable organisms 2)Allows use of appropriate empiric antimicrobial therapy 3)Doesn't give information on: Antimicrobial susceptibility/Typing 4)fastest method
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What are the principles of immunological tests?
1) antibody detection- IgM detection/ seroconversion/fourfold rise in titre 2) other immunological tests-IFN-γ release assays in tuberculosis
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What is seroconversion?
Change from negative to positive result from one test to a subsequent test
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Explain fourfold rise in titre
Rise in concentration of antibody from one test to a subsequent test “Titre” is 1/greatest dilution at which antibody is detectable i.e. if antibody is just detectable at a serum dilution of 1/64, the titre is 64 “Fourfold rise in titre”=2 →32/4→64
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What are the uses and limitations of antibody testing?
1)Confirms exposure to a specific micro-organism Cultivable and nun-cultivable organisms 2)Is restricted to patients with a detectable antibody response 3) Is retrospective Often too late to inform antimicrobial therapy decisions
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Other cards in this set

Card 2

Front

What are the symptoms of a temperature?

Back

1) fever (burning up) 2) chills, sweats, night sweats 3) rigors

Card 3

Front

What are the 2 reasons to carry out a diagnostic test?

Back

Preview of the front of card 3

Card 4

Front

What is in a full blood count?

Back

Preview of the front of card 4

Card 5

Front

What does haemoglobin show?

Back

Preview of the front of card 5
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