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3.0 Microbiology > CSF > Flashcards

CSF Flashcards

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1
Q

How many CSF samples should be taken and why?

A

Best practice to take 3+ samples
3+ samples required for a serial red cell count

This might not always be possible, depends on how well the patient can tolerate it etc
Might get 5+ samples depending

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2
Q

Why do we do a serial red cell count

A

Gives us information on how traumatic a tap was

Red cells should be highest in the first sample but should decrease with each sample

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3
Q

What would high red blood cells in each sample indicate

A

Subarachnoid haemorrhage

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4
Q

Why would a random sample have an increased red cell count

A

Might be due to movement of the patient or movement of the needle etc

There might be high red cells in 2 or 3 of the samples if there was poor access etc

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5
Q

When do we a serial red cell count

A

Done on all samples as long as there is 3+ samples

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6
Q

If you have 6 CSF samples which ones do you use? Why?

A

Use the last three samples
i.e. the ones labelled 4, 5, 6

Least amount of red blood cell contamination

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7
Q

How do we process a CSF sample

A

Describe the appearance of all CSF samples

White cell count + Diff if necessary

Supplemental tests

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8
Q

How do we describe the appearance of CSF

A

Colourless
Blood stained
Xanthochromia
Spider-web clot

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9
Q

What does Xanthochromia mean?

A

Straw coloured CSF

Due to the breakdown of bilirubin

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10
Q

What does a spider web clot in a CSF indicate?

A

TB meningitis

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11
Q

What sample do we carry out a white cell count on? Why?

A

Last sample

Most accurate count, it’s directly from patient, least contamination

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12
Q

What is considered a high white cell count for CSF?

A

White cell counts of 5 or higher

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13
Q

What is considered a high red cell count?

A

Red cell count of 10 or higher

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14
Q

What would a CSF with a wcc >5 look like?

A

Cloudy in appearance

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15
Q

What can be done if the red blood cells are really high? Why

A

Use Turk’s solution

This dissolves any red blood cells

This allows for a more accurate white blood cell count

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16
Q

What do we do if a white blood cell count is greater than 5?

A

We carry out a differential stain

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17
Q

How do we carry out a differential stain?

A

Count the number of mononuclear cells versus polynuclear cells

18
Q

What does high mononuclear cells in a CSF diff mean

A

Viral infection

19
Q

What does high polymorphonuclear in a CSF diff mean?

A

Bacterial infection

20
Q

Do we do gram stains for CSF?

A

No gram stains
We do a film array instead

21
Q

Give some examples of internal supplemental test

A

Biochemistry for protein and glucose
Immunology for monoclonal bands

22
Q

Give some examples of send outs

A

MS investigation -> send out to UK

Alzheimer’s investigation -> send out to UK

Xanthochromia -> samples sent to Beaumont in a dark tube or wrapped in tinfoil

Query CJD sent out to Beaumont

Beta-2-transferrin sent to UK

23
Q

How are glucose and protein affected in bacterial vs viral infection?

A

Glucose decreased and protein increased during bacterial infection

Less of an impact seen during viral infection -> increased protein only

24
Q

Why might we test for Beta-2-transferrin?

A

Used to test if a sample contains any CSF

Maybe a patient has a query CSF leakage -> want to confirm is CSF

Non done in house, sent to the UK

25
Q

When do we culture CSF

A

Only done if cultures are wanted
-> bacterial meningitis

No need if viral meningitis etc

26
Q

What do we culture CSF on

A

Chocolate and blood agar

27
Q

When do we read CSF plates

A

Read twice
Once after 24 hours
Once after 48 hours

28
Q

What discs do we put up on CSF plates?

A

No discs
If any colony grows its significant

29
Q

Why might we not see any growth when we culture CSFs up

A

Patients are nearly always on antibiotics already

This is why we use the film array

30
Q

What is the principle behind the film array?

A

Nested PCR

31
Q

What are the benefits and disadvantages of using Film Array?

A

Useful for CSFs which are usually culture negative

Only downfall is that sensitivities cannot be done

32
Q

What film array panels do we use

A

Two panels:
- Meningitis/Encephalitis panel
- Respiratory panel

33
Q

When do we use the film array respiratory panel?

A

▪ Done for someone suffering from flu symptoms who is Covid negative and GeneXpert negative
▪ Not very common, only done to try and figure out what exactly the patient has
Panel containing covid and adenovirus etc

34
Q

What do we do if the film array is unable to type the virus?

A

We send the sample to the NVRL for typing

35
Q

What should we be looking for in CSF for HIV/Transplant patients

A

Cryptococcus
We do a cryptococcus antigen screen on all newly diagnoses HIV patients

36
Q

What are the common causes of bacterial meningitis in adults

A

H. influenzae
S. pneumoniae
N. meningitidis

37
Q

What is the most common cause of viral meningitis?

A

70% is enterovius

38
Q

What are some different types of meningitis

A

Bacterial
Viral
Cryptococcal meningitis
TB meningitis -> very rare in Ireland

39
Q

What are some common causes of meningitis in MMUH

A

S. pneumoniae
Haemophilus. influenzae
Neisseria species including N. gonorrhea

Enterovirus
Herpes caused meningitis

40
Q

What would indicate a cryptococcal infection?

A

Large volume of CSF
6+ samples etc

41
Q

What is the most common cause of meningitis in children?

A

Adenovirus

42
Q
A

3.0 Microbiology (21 decks)

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