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Flashcards in Diagnosis of an Infection Deck (60)
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1
Q

What general symptoms are seen with infections?

A
  • Pyrexia
  • General malaise
  • Rash
  • Headache, abdominal, or respiratory symptoms
  • Septic shock
2
Q

What may the pattern of pyrexia be specific to?

A

Different infective causes

3
Q

What conditions, other than infections, can cause pyrexia?

A
  • Malignancy
  • Drugs
  • Other diseases
4
Q

What is meant by general malaise?

A

Flu-like symptoms

5
Q

What does general malaise result from?

A

Cytokines

6
Q

When is septic shock produced?

A

Severe infection

7
Q

What may the site of the actual infection show?

A
  • Local pain
  • Discharge
  • Coughs
  • Sputum production
  • Diarrhoea
8
Q

How can infectious agents be categorised?

A
  • Toxin mediated
  • Acute pyogenic
  • Sub-acute
  • Chronic granulomatous
9
Q

What is it important to consider when looking at infection to give a better understanding of the disease?

A

The exposure to the likely source

10
Q

What are the categories potential exposures to the source?

A
  • Endogenous
  • Exogenous
11
Q

What should be do when it is suspected an individual has an infection?

A
  • History taken
  • Clinical examination
  • Samples for microbiological testing
12
Q

What is the purpose of the history and clinical exam when an individual is suspected to have an infection?

A

So a differential diagnosis can be produced

13
Q

What types of specimen can be taken for microbiological investigation?

A
  • Blood
  • Pus
  • Lavage
14
Q

What should happen once a specimen has been taken?

A

It should be cultured

15
Q

Why should a specimen be cultured when taken for clinical examination?

A

To increase the number of microbes grown for identification

16
Q

What can cultures be used to do?

A

Limit the growth of certain pathogens to reduce any contaminants in the sample

17
Q

How may a clinical sample for investigation get contaminated?

A

Poor aseptic technique obtaining the sample

18
Q

What potential problem could arise when trying to culture a sample for microbiological investigation of an infection?

A

Many organisms are obligate anaerobes, which will be killed in exposure to an atmosphere with oxygen

19
Q

What is required for viruses to grow?

A

A cell culture

20
Q

What should happen following the obtaining of a clinical specimen?

A

The sample must be analysed

21
Q

What are the categories of mechanisms for analysing a clinical specimen?

A
  • Microscopy
  • Molecular techniques
  • Serology
22
Q

How can the sample be analysed microscopically?

A

Via various staning or flouresence

23
Q

What stain is used for bacteria?

A

A gram stain

24
Q

For what bacteria can a gram stain not be used?

A

Mycobacterium

25
Q

What stain is require to examine mycobacterium microscopically?

A

ZN stain

26
Q

What samples can be examined microscopically directly (with no stain)?

A

Stool samples

27
Q

What can be indentified when examining a stool sample directly?

A

Parasites

28
Q

What can be used for viral detection?

A

Electron microscopy

29
Q

What can be used to diagnose RSV?

A

Flouresence

30
Q

What is the main molecular technique used in microbiological examination?

A

Nucleic acid amplification testing (NAAT)

31
Q

What is NAAT used to identify?

A

Both bacteria and viruses

32
Q

How does NAAT work?

A

It amplifies target DNA or RNA, until sufficient quantities have been cultured, and machines can then test the nucleic acid and identify the species

33
Q

What is NAAT very useful for?

A

Organisms that are slow growing or dangerous to grow

34
Q

What is serology?

A

Testing for the blood serum for an immune response against a specific pathogen

35
Q

How is a diagnosis made using serology?

A

By detecting a rise in antibody levels, or the presence of an IgM antibody

36
Q

What techniques of serology are used?

A
  • Agglutination
  • Enzyme immunoassay
  • Complement fixation
37
Q

What does agglutination involve?

A

The clumping together of antibodies to produce a large group, which can then be identified to identify the bacteria involved

38
Q

What happens in enzyme immunoassay?

A

Antibodies specific for the IgG antibodies for certain reactions are on a solid support, and will produce a response if they bind to the specific IgG antibody for the certain microbe

39
Q

What are antibody levels often quoted as?

A

Titres

40
Q

What are titres?

A

The reciprocal of the last dilution at which Ag-Ab complex could be detected

41
Q

What should be done if the laboratory findings do not match the clinical findings?

A

The laboratory results should be questioned for a potential false positive

42
Q

What is it important is done for the final diagnosis?

A

The microbiology is matched to the clinical findings

43
Q

What can be done following identification for some bacteria and fungi?

A

Check the antibiotic susceptibility

44
Q

How can bacteria be classified?

With regards to antibiotic susceptibility

A
  • Susceptible
  • Moderately resistant
  • Resistant
45
Q

What is meant by a susceptible bcateria?

A

One where a normal dose of antibiotic results in cure

46
Q

What is meant by a moderately resistant antibiotic?

A

One where a large dose of antibiotic results in cure

47
Q

What is meant by resistant antibiotic?

A

One where antibiotics are likely to fail

48
Q

What is the main technique for determining antibiotic susceptibility?

A

Grow the culture in medium, and placing antibiotic impregnanted disks into the medium and measuring the diameter on inhibition on the plate

49
Q

What does testing for antibiotic susceptibility provide?

A

An estimate into how well the patient will react to therapy

50
Q

What is the limitation of testing for antibiotic susceptibilty?

A

The clinical response will also depend on host factors

51
Q

Other than using discs, how can antibiotic susceptibility be checked?

A

Using broth dilution tests

52
Q

What do broth dilution tests provide?

A
  • A minimum inhibitory concentration (MIC)
  • A minimum bactericidal concentration (MBC)
53
Q

What is the minimum inhibitory concentration?

A

The minimum concentration of antibiotic that can be given to inhibit growth

54
Q

What is the minimum bactericidal concentration?

A

The minimum concentration of an antibiotic that can be given to kill the bacteria

55
Q

Label this picture of a broth dilution test

A
  • A - Minimum Inhibitory Concentration
  • B - Minimum Bactericidal Concentration
  • C - Growth on subculture
56
Q

What are the advantages of culture dependant identification?

A
  • Can test other properties
  • Sensitive and specific
57
Q

What other properties can be tested for using culture dependant identification?

A
  • Sensitivity
  • Virulence
  • Phenotype
58
Q

What are the disadvantages of culture dependant identification?

A
  • Slow
  • Organism must be alive
  • Low yield post-antibody response
  • Method often highly organism specific
59
Q

What are the advantages of culture independant identification?

A
  • Rapid
  • Organism can be alive or dead
  • Suitable after antibody response
  • Sensitive
60
Q

What are the disadvantages of culture indepedant identification?

A
  • Limited testing of other properties
  • Potential for contamination
  • Same methods apply to all organisms