Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microorganisms + Disease > Laboratory diagnosis L7 L9 > Flashcards

Laboratory diagnosis L7 L9 Flashcards

1
Q

what are the functions of diagnostic microbiology labs

A

Detection, isolation, identification of disease causing microorganisms
Antibiotic sensitivity testing as a guide to therapy and monitoring resistance patterns
Serological analysis to detect antibody responses associated with infection or to detect antigens in clinical specimens
Information used locally to guide treatment/regionally if there is an outbreak

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is serology

A

Look for evidence for immune response – detect antibody response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is surveillance for

A

emerging patterns of antibiotic resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

are bacteria always reported if found

A

Mandatory reporting e.g C.difficile, S.aureus bloodstream infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what types of research are used in diagnostic microbiology labs

A

molecular approaches to supplement or replace existing detection or identification methods to improve speed of diagnosis
molecular methods is quicker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is a request form for

A

completed request form is a request for consultation or referral for a specialist opinion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is analysed in a lab after form complete

A

Origin (site) of specimen determines likely pathogens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what determines the procedures done in a lab after form complete

A

Depending on the type of specimen determines the procedure for processing
(microscopy, culture medium, identification, antibiotic sensitivity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what determines the urgency and priority of processing samples

A

clinical details

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is a common infection

A

gastrointestinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does gastrointestinal infection cause

A

usually get diarrhoea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

examples of bacteria that cause gastrointestinal infection

A 
Campylobacter
Salmonella
Escherichia coli
Shigella sp.
Clostridium difficile
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

examples of viral causes of gastrointestinal infection

A 
Rotavirus
adenovirus
norovirus
astro-
calici-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

examples of parasites that cause gastrointestinal infection

A

Cryptosporidium sp.
Giardia lamblia
Entamoeba histolytica

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what specimen is used to study gastrointestinal infections

A

liquid stool

Generally when diarrhoea goes organisms tend to go

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

why is vomit not usually used as a sample

A

Stomach and back of throat in vomit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

why are samples generally collected at the start of infection

A

organisms start to drop off when begins to clear – harder to find organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are details of the patients history important

A 
need to know if travelled
acute
chronic
symptoms
is caught in hospital
etc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how can stool samples be examined

A 
Macroscopic appearance
Selective Culture
Microscopy
PCR/ slide agglutination
PCR/EIA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is Macroscopic appearance used for in stool examination

A

liquid, blood-stained, ‘rice-water’ etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is selective culture used for in stool examination

A

only specific bacteria will survive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is microscopy used for in stool sample examination

A

for ova, cysts and parasites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is PCR /slide agglutination used for in stool sample examination

A

for viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is PCR/EIA used for in stool sample examination

A

C. difficile and its toxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what does stool mainly contain, what problem does this cause

A

contains mostly commensal bacteria – detecting the pathogen is the challenge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how is salmonella / shigella examined

A

used DCA orXLD agar
Prior enrichment using Selenite broth – may also be used on food
Colonies identified using slide agglutination and biochemical tests

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how is campylobacter examined

A

Agar containing vancomycin, polymyxin B & trimethoprim. Kill all except campylobacter
incubated 42 degrees Colonies identified by oxidase test
and Gram film appearance vibrio like shaped cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

why is campylobacter incubated at 42 degrees

A

body temp of chicken, where it is found

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what agar is used to grow Vibrio cholerae

A

Thiosulphate-citrate-bile salt-sucrose (TCBS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is Vibrio cholerae enriched in

A

alkaline peptone water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what happens to Vibrio cholerae when grown on TCBS plate

A

ferments sucrose and produces yellow colonies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what are the two test stages in C. difficile detection in stool sample

A

Stage 1 - Screening (non specific)
a) Detection of toxin genes - PCR (or nucleic acid testing NAATs)
b) Detection of glutamate dehydrogenase enzyme – Enzyme immunoassay
Stage 2 - Confirmation
Confirmation of toxin production using an enzyme immunoassay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

how are intestinal helminth ova detected in stool sample microscopy

A

Microscopy to detect helminths and protozoa– stool concentrated and examined mixed with Lugols iodine or stained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what types of intestinal helminth ova are there

A

roundworm

whipworm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

how are viruses usually examined in a stool sample

A

PCR based molecular methods

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is the old way that viruses were detected in stool samples

A

electron microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what is the downside of electron microscopy

A

expensive, time-consuming, insensitive only looking at a tiny amount under microscope, if there is not a lot of the virus may miss it and misdiagnose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what is slide agglutination

A

latex particles coated with rotavirus-specific monoclonal antibody)
used to detect viruses in stool samples

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

when are UTIs common

A

women and children

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what causes UTIs

A

Cystitis or pyelonephritis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what can recurrent infections in children cause

A

renal damage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what are the symptoms of UTI

A
  • dysuria (pain when go toilet)
  • frequency (need to often go toilet)
  • secondary enuresis (bladder leaking)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is the most common cause of UTIs

A

E.coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

when are microbiological diagnosis’ required

A
  • in children (risk of renal damage)
  • recurrent UTI (resistant organisms likely)
  • in males (UTI much less common & often -indicates other pathology)
  • if pyelonephritis is suspected (fever/loin pain)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what are the ways urine is sampled

A

Midstream urine (MSU) not the first bit of urine the bit after
‘Clean- catch’ or ‘bag’ urine young children can’t always produce urine on demand
Catheter urine (CSU)
Suprapubic aspirate (SPA)
Nephrostomy / Ureteric urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what can be used to test urine

A

Dipstick for blood, nitrite, leukocyte esterase
put stick into urine
wait for colour changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what is the downside of using dipstick method for urine examination

A

not always accurate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what does a high number of RBC indicate

A

haematuria

49
Q

what does a high number of WBC indicate

A

infection

50
Q

what does a high number of epithelial cells indicate

A

contamination

51
Q

how are bacteria isolated for urine example

A

Semi-quantitative culture using CLED agar or Chromogenic media
antibiotic sensitivity testing

52
Q

what is Sterile pyuria

A

presence of high numbers of WBCs

WBCs suggest infection but no bacterial growth obtained

53
Q

what causes sterile pyuria

A

Antibiotic treatment prior to specimen collection
Catheterisation
Tumour
Urine infection with fastidious
Vaginal discharge / urethritis (e.g. Chlamydia) (wouldn’t detect on agar plate)
Renal tuberculosis (wont grow under normal conditions used)

54
Q

what is the problem of using antibiotic treatment before collect sample

A

already killed the organism

55
Q

why may catheterisation cause ‘infection’

A

it causesinflammation not infection

56
Q

why might tumour think is infection

A

WBC in urine

57
Q

what is fastidious and the problem it causes

A

wouldn’t normally grow under media used, would need special conditions to grow it organism e.g. mycoplasma

58
Q

what are the specimens collected for wound infections

A

pus
tissue
body fluid
all superior to swabs

59
Q

how should swabs be taken

A

taken from as deep as practicable within the substance of the lesion. Send to the laboratory in special ‘transport medium’

60
Q

how should the specimen be cultured

A

aerobically an anaerobically

61
Q

what should be done to identify bacteria in infections

A

test antibiotic sensitivity coagulase Lancfield etc

62
Q

what type os agars are used to streak bacteria to identify from wounds

A

Use fairly rich agars (non-selective media) which will allow most bacteria to grow, so have a change to isolate bacteria

63
Q

what is URTI

A

upper respiratory tract infection

64
Q

examples of URTIs

A

Otitis media
sinusitis
pharyngitis
tracheitis

65
Q

how common are URTIs

A

Very common; often viral in aetiology

66
Q

what is URTIs severity

A

Relatively minor, but if get into lung is very serious

67
Q

what is LRTI

A

Lower respiratory tract infection

68
Q

examples of LRTIs

A

Bronchitis
bronchiolitis
pneumonia

69
Q

what may cause LRTIs

A

May be bacterial, viral or fungal in aetiology

70
Q

what is the history of the patient important for in LRTIs

A

to determine likely pathogens

71
Q

examples of community acquired pneumonia

A 
Streptococcus pneumoniae 
Haemophilus influenzae
Staphylococcus aureus (post ‘flu)
Mycoplasma pneumoniae 
Legionella pneumophila
72
Q

examples of hospital acquired pneumonia

A

Coliforms (e.g. E. coli, Klebsiella sp., Enterobacter sp.)
S. aureus (MRSA)
Pseudomonas aeruginosa

73
Q

examples of respiratory tract infection specimens

A 
throat swab
sputum
tracheal aspirate
pernasal swab 
urine antigens 
acute and convalescent serum
74
Q

where must a throat swab be from

A

pharynx

75
Q

where must a sputum swab be from

A

NOT Saliva only from mouth not from lung)

May be obtained after chest physiotherapy as some cant cough up well e.g. cystic fibrosis

76
Q

how must a tracheal aspirate be taken

A

taken from ventilated patients in Intensive care

77
Q

what is a pernasal swab for

A

Designed to obtain optimum sample for culture of Bordetella pertussis (Whooping cough)

78
Q

what does an acute and convalescent serum detect

A

When first have disease then later on too see change in antibodies
Detection of pathogen-specific antibodies
it is slow

79
Q

if cannot cough how are respiratory tract infections done

A

may need a more invasive method

80
Q

what precautions must be taken when performing respiratory sample examination

A

All processing performed in a high level - Category 3 containment lab (due to TB risk
Samples handled in a Class 1 safety cabinet (delivers a negative pressure environment)
Gown & gloves are worn

81
Q

how is sputum examined

A

Sputum microscopy
Gram stain: pus cells, organisms (historical)
Ziehl-Neelsen (ZN) stain for Mycobacteria

82
Q

what must be added to sputum and why

A 
Sputum very sticky so add something to dilute it down and remove other organisms present
Sample diluted (reduces growth of commensal oropharyngeal organisms)
83
Q

what contaminates sputum

A

Sputum gets contaminated by things in the mouth when coughed up too

84
Q

how are respiratory samples cultured

A

Cultured on selective and non-selective agar plates to maximise the chances of finding organisms

85
Q

what stain is first used in TB microscopy

A 
Auramine staining (UV microscopy)
Detect with microscope
86
Q

why is a second stain required in TB microscopy

A

auramine stain sensitive but not very specific for mycobacteria so do the ZN stain to confirm it
ZN stain always used to confirm auramine positive samples will be red

87
Q

how is TB culture decontaminated

A

using sodium hydroxide
treat sputum with NaOH will kill most bacteria
Mycobacterium Tb has a thick waxy coat so survives the NaOH
Is then plated onto special media

88
Q

how long does it take for TB plated cultures to grow

A

Solid agar slopes (Lowenstein-Jenson media): 6-8 weeks to grow

89
Q

how long does it take for TB liquid cultures to grow

A

Liquid culture using Mycobacteria Growth Indicator Tube (MGIT): 1-2 weeks or less

90
Q

what is immunofluorescence

A

using organism-specific monoclonal antibodies linked to a fluorescent dye
When antibodies bind to bacteria it makes them fluoresce

91
Q

what colour is lactose fermenting bacteria and which plate is this on

A

pink

MacConkey agar

92
Q

what is bacteraemia

A

Positive blood culture (blood is normally sterile)

93
Q

what can cause bacteraemia

A

infected organs, abscesses, catheters etc

may have transient bacteraemia from tooth brushing

94
Q

what is sepsis

A

blood poisoning

bacteria is growing in the blood

95
Q

what is the most common cause of sepsis

A

E.coli

96
Q

what is infective endocarditis

A

Infection of heart valves – affects function and may be lethal

97
Q

what happens to heart valves in infective endocarditis

A

Heart valves are colonised by bacteria circulating
in the blood, if previous damage to the heart valve makes hem sticky and bacteria can stick, forms “vegetations” on the heart valves

98
Q

what happens once infective endocarditis occurs

A

Once infection is established, bacteria or parts of the vegetation may break away from the valve and enter the bloodstream

99
Q

how is infective endocarditis diagnosed

A

So analysis of blood cultures is also used in diagnosis of infective endocarditis

100
Q

how is the specimen obtained for analysis of blood cultures

A

up to 10 ml venous blood from patient using aseptic techniques to not contaminate the blood/bottle; 2-3 separate sets taken at different times during the day, bacteria numbers may change during the day; should collect before starting antimicrobial therapy; transport immediately.

101
Q

once the blood cultures are obtained what happens to the bottles

A

Bottle contains growth medium add the blood
Incubate bacterial bottles at 37 degrees
Detects metabolites, incubator will signal result

102
Q

what tests are done on blood cultures to analyse them

A

subculture onto various agar media under different conditions
antibiotic sensitivity
gram stains
identify bacteria using e.g. AP1 test

103
Q

what is CSF

A

Cerebrospinal fluid

104
Q

what does CSF look like

A

Clear, cloudy, bloody, purulent

105
Q

how is a CSF sample taken

A

collected in a sterile bottle under aseptic conditions

Taken immediately to the laboratory, day or night. (Blood cultures must be taken)

106
Q

how is CSF measured

A

Total cell count, different cell types (e.g. neutrophils, lymphocytes), proteins, glucose – differ for bacterial and viral meningitis

107
Q

what is done to CSF to make a gram film

A

CSF is centrifuged and the deposit stained. It may or may not be positive

108
Q

what type of cultures are CSFs grown on

A

eposit on various rich agars (e.g. blood and chocolate agar) and incubate under different conditions (CO2, aerobically, anaerobically)

109
Q

how is viral meningitis diagnosed

A

PCR of CSF, stool & throat swabs

110
Q

how are rarer forms of TB meningitis diagnosed

A

TB meningitis - Ziehl-Neelsen film and special culture methods
Cryptococcal meningitis - India ink ‘wet’ film to demonstrate capsule

111
Q

what will the CSF be like if infected with bacteria

A

clear/turbid
many neutrophils (more WBC)
more protein
less or no glucose as transporters interfered with

112
Q

what will the CSF be like if infected with virus

A

clear
increased lymphocytes
normal or more proteins
normal glucose

113
Q

what causes meningitis

A

different bacteria depending on age

114
Q

what can still affect meningitis infected people when recover

A

Even if recover can cause long lasting problems e.g. losing limbs due to coagulation neurological, hearing problems
Not just the initial infection that is the problem

115
Q

what still requires a bacteria culture

A

antibiotic sensitivity testing

116
Q

what will PCR detect even if dead

A

PCR will detect bacterial DNA even if the bacteria have already been killed by antibiotic treatment

117
Q

how is bacteria identified in sterile sites

A

Sometimes although infection is suspected, causative organism cannot be grown in culture e.g joint fluids
PCR is used to amplify 16S Ribosomal RNA genes, these contain conserved regions and sequences unique to individual bacterial species
DNA sequence analysis of PCR amplified DNA allows identification of the specific bacterium causing infection

118
Q

how is Maldi-Tof identified

A

Each organism has a unique pattern made in mass spectrometer

compare against a database

Microorganisms + Disease (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions