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X Infectious Diseases > Diagnosis Of Infectious Diseases > Flashcards

Diagnosis Of Infectious Diseases Flashcards

1
Q

Give examples of artificial media

A

Solid agar media
Liquid culture media
Tissue culture

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2
Q

For pathogens, how are they categorised?

A

Hazardous groups 1-4

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3
Q

What hazard group do S. aureus, Strep. pyogenes and Vibrio cholerae belong to?

A

Hazard group 2

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4
Q

What hazard group do Bacillus anthracis, Hepatitis B virus, Mycobacterium tuberculosis, Salmonella typhi and West Nile Virus belong to?

A

Hazard group 3

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5
Q

What does Mycobacterium tuberculosis stand for?

A

TB

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6
Q

What is another name for Salmonella typhi?

A

Typhoid fever

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7
Q

What is another name for West Nile Virus?

A

Encephalitis

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8
Q

What hazard group do Ebola virus, Dengue virus, Haemorrhagic viruses and Variola virus belong to?

A

Hazard group 4

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9
Q

What is another name for Variola virus?

A

Small pox

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10
Q

What are the different types of artificial media used for?

A

Used to classify pathogens

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11
Q

What does Mycobacterium leprae cause?

A

Leprosy

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12
Q

How can you directly diagnose a sample from a patient?

A

Culture microbe from a specimen

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13
Q

How can you indirectly diagnose a sample from a patient?

A

Find evidence of an antibody response in a patient’s serum

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14
Q

What 6 things are important in taking a specimen?

A
  • Pre treatment
  • Appropriate site
  • Enough material
  • Appropriate container
  • Rapid transport
  • Transport medium
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15
Q

What 7 types of specimens are there?

A
  • Swabs
  • Urine
  • Faeces
  • Sputum
  • CSF
  • Blood (culture)
  • Blood (serum)
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16
Q

When should you collect specimens?

A
  • before antibiotics
  • depends on disease e.g. malaria take sample at spiking fever - parasites into blood
  • serology - second sample 2 weeks later to look for antibody titres
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17
Q

What information needs to be given with the sample?

A
  • type of specimen/site
  • date and time of collection
  • date of onset of illness
  • age/gender
  • details of illness/history
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18
Q

What difference is there in infected urine and CSF?

A

cloudy

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19
Q

What difference might there be in sputum?

A

pus in sputum

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20
Q

What general bacteriology diagnostic tests are there?

A
  • microscopy
  • culture
  • identification
  • antimicrobial susceptibility testing
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21
Q

What 7 kinds of non-cultural techniques/microscopy are there?

A
  • wet preps
  • gram stain
  • acid fast stain
  • fluorescent antibody stains
  • phase contrast microscopy
  • dark field microscopy
  • inverted microscopy
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22
Q

What colour is the acid fast stain of sputum?

A

pink

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23
Q

Acid fast stain - what is a good pathogen that stains?

A

TB

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24
Q

Examples of pathogens that are stained: dark field microscopy of spirochaetes

A

lyme disease

syphillis

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25
Q

Examples of pathogens that are stained: phase contrast

A

yeast

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26
Q

Examples of pathogens that are stained: inverted microscope

A

tissue culture

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27
Q

What other non-cultural techniques are there?

A
  • serology

- molecular methods - gene probes

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28
Q

What is serology?

A

look for an antibody response to the organism over a couple of weeks

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29
Q

What different serology techniques are there?

A
  • agglutination (plate/slide)
  • immunofluorescence
  • complement fixation
  • ELISA
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30
Q

What can an agglutination plate be used to diagnose?

A

Flu

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31
Q

How does ELISA work?

A

Colour change - makes it easier to identify - use plate reader

32
Q

When would you use PCR?

A
  • determining outbreaks
  • quick result e.g. TB
  • probe for toxin e.g. cholera toxin in faeces
33
Q

When is TB PCR used?

A
  • developed counties
  • to look for drug resistant strains
  • result within hours
34
Q

What is the downside to TB PCR?

A

expensive

35
Q

What types of non-selective media are there?

A
  • blood agar
  • chocolate agar
  • liquid media, as in blood cultures
36
Q

What typically grows on chocolate agar?

A
  • more ‘fastidious’ pathogens

e. g. Neisseria, Haemophilus - usually incubated in CO2

37
Q

How are organisms grown in liquid media?

A
  • one anaerobic
  • one aerobic
  • one subcultured
38
Q

What is selective media?

A

Contain substances which inhibit the natural flora or select for certain organisms

39
Q

Is Maconkey selective or non-selective?

A

Selective

40
Q

What does Maconkey contain?

A

Bile salts and lactose

41
Q

Why does Maconkey contain bile salts and lactose?

A

Select for gut organisms

42
Q

What sites is Maconkey selective for?

A

abdominal wounds

43
Q

What specimens is XLD agar selective for?

A

faeces

44
Q

Is XLD selective or non-selective

A

selective

45
Q

what does XLD contain?

A

xylose, lysine and deocycholate

46
Q

How do you grow genital specimens?

A

grow on chocolate with antibiotics to select for particular organism

47
Q

if the organism grown on maconkey ferments lactose, what colour does the agar change?

A

red

48
Q

if the organism grown on maconkey does not ferment lactose, what colour does the agar change?

A

pinky

49
Q

what is an example of an organism that maconkey is selective for, and ferments lactose?

A

e.coli

50
Q

what does maconkey differentiate between?

A

lactose fermenters and non-lactose fermenters

51
Q

what colour is shigella on XLD?

A

pink

52
Q

what colour is salmonella on HEK?

A

blue

53
Q

what final ID tests are there?

A

API (biochemical)

agglutination e.g. staph ID or strep grouping

54
Q

coagulase test - is staph aureus positive or negative?

A

positive

55
Q

coagulase test - is staph epidermidis positive or negative

A

negative

56
Q

if the suspected pathogen is a staph, what media should be used?

A

mannitol salt

57
Q

if the suspected pathogen comes from an abdominal wound swab, what media should be used?

A

maconkey

58
Q

if the suspected pathogen comes from a skin sample, what media should be used?

A

mannitol salt?

59
Q

if mannitol salt turns yellow, what is it likely to be?

A

staph aureus

60
Q

if mannitol salt turns pink, what is it likely to be?

A

staph epidermidis, but this is probably not the pathogen

61
Q

2 examples of anaerobes

A

clostridium perfringens

bacteroides fragilis

62
Q

for urine specimens, what does a dipstick measure?

A

sugar in urine

63
Q

why do a microscopy-cell count of a urine sample?

A

count white blood cells for a sign of infection

64
Q

if the dipstick is positive for nitrates and proteins, what should you do?

A

culture the sample

65
Q

how can you identify bacteria?

A
  • size
  • colour
  • shape
  • biochemical tests
  • antibiotic sensitivity to aid ID
66
Q

would you gram stain a faeces sample? why?

A

no - too many organisms

67
Q

what is the problem with gram staining e.coli and salmonella?

A

they look the same!

68
Q

what tests do you do on faeces samples?

A
  • culture

- microscopy for parasites

69
Q

what media should you use for faeces samples? what should they contain?

A

need bile salts

  • XLD
  • HE
  • maconkey isn’t very selective
70
Q

for a sputum sample, what tests should you do?

A
  • microscopy
  • culture

look at the microscopic appearance - does it contain pus or is it just saliva?

71
Q

if you are looking for TB in a sputum sample, what tests should you request?

A

specialist agar

separate TB request

72
Q

when collecting a CSF sample, how should you collect it and what should you do with it?

A

3 separate tubes
tubes 1 and 2 to cytology
3 to microbiology - less chance of contamination

73
Q

when you suspect meningitis in a patient, what tests should you do?

A

microscopy
gram stain
culture to check antibiotics

74
Q

what tests do you do after culturing the organism?

A
  • identification - need a pure culture
  • biochemical tests (APIs), lactose fermentation
  • antigen/antibody tests (usually latex beads that clump together
  • molecular methods - DNA fingerprinting etc
75
Q

how can you test viruses?

A
  • electron microscopy
  • immunofluorescence microscopy
  • culture in tissue culture
  • growth in eggs

X Infectious Diseases (9 decks)

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