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Neurology > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is meningitis

A

Inflammation of the meninges

all layers

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2
Q

What can an untreated CNS infection lead to

A

Brain herniation - death

Cord compression and necrosis - leads to paralysis

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3
Q

Location of a brain infection determines the symptoms - true or false

A

TRUE

Depends where in the brain is affected and what it is responsible for

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4
Q

What is encephalitis

A

Infection of the whole brain

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5
Q

How does pyogenic meningitis appear

A

Pus forming - get a thick suppurative layer on the brain

Would see lots of neuropils microscopically and in LP

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6
Q

What are the classifications of meningitis

A

Acute pyogenic - bacterial
Acute aseptic - viral
Acute focal suppurative infection - abscess or empyema
Chronic bacterial infection 0 TB

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7
Q

What is the treatment for bacterial meningitis

A

Ceftriaxone IV
Must give steroids with the antibiotics - dexamethasone
For the over 60s or the immunocompromised you must add in amoxicillin to cover for listeria

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8
Q

What is the most common organism that causes bacterial meningitis

A

Strep pneumo

Listeria also common in the elderly or immunocompromised

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9
Q

If a patient with meningitis has recently travelled to a country with high penicillin resistance, what should be included in their treatment

A

Vancomycin

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10
Q

How do you diagnose viral meningitis

A

Viral stool culture
Throat swab
CSF PCR

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11
Q

How do you treat viral meningitis

A

Treat symptomatically – anti-emetic, rehydration etc

Usually self limiting so treat supportively

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12
Q

What are the clinical features of encephalitis

A 
Confusion, change in mental state 
May have neck stiffness or other 'meningitis' symptoms 
Stupor or coma 
Seizures
Partial paralysis 
Speech and memory symptosm
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13
Q

Encephalitis has a fast onset - true or false

A

False

Usually insidious - takes a few days to a week

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14
Q

What investigations would you do for encephalitis

A

LP
EEG
Blood cultures
CT/MRI -will see changes

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15
Q

What viral cause of encephalitis must you rule out before treating with antibiotics

A

Herpes simplex

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16
Q

Do you get MRI changes in meningitis

A

NO

You do with encephalitis - differentiates between them

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17
Q

What are the common signs and symptoms of bacterial meningitis

A 
Fever 
Cold peripheries 
Vomiting 
Drowsiness and lethargy
Confusion and irritability 
Non- blanching rash 
Severe muscle pain and headache 
Stiff neck 
Photophobia 
Convulsions and seizures
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18
Q

What are the risk factors for bacterial meningitis

A

Immunosuppression - listeria risk
Neurosurgery or head trauma - staph risk
Fracture of the cribriform plate - strep pneumo

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19
Q

Which organism is the most common cause of bacterial meningitis in neonates

A

Listeria
This is why pregnant ladies shouldn’t eat certain cheeses etc
Also strep pneumo

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20
Q

Which organism is the most common cause of bacterial meningitis in children

A

Haem influenza

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21
Q

Which organism is the most common cause of bacterial meningitis in teenagers and young adults

A

Neisseria meningitidis

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22
Q

Which organism is the most common cause of bacterial meningitis in adults

A

Strep pneumoniae

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23
Q

Which organism is the most common cause of bacterial meningitis in the elderly

A

Strep pneumoniae and listeria

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24
Q

What are some of the lifelong consequences of a meningitis

A 
Limb loss 
Deafness 
Mental impairment 
Blindness 
Cerebral palsy

These will affect around 25% of those who survive meningitis

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25
Q

Which cranial nerves are vulnerable to damage in meningitis

A

III and VI

If pus collects around them they can be damaged

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26
Q

Describe the pathogenesis of bacterial meningitis

A

The bugs can come from nasopharyngeal colonization
They can travel from sinusitis, mastoiditis or across skull fracture to reach the brain
Remote focal infections can also track up to the brain - pneumonia etc

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27
Q

Which bacteria can cause meningitis in the immunocompromised population

A

The typical agents - strep and staph - can still affect
Listeria
TB
Cryptococcus is seen in HIV with a low CD4+

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28
Q

What treatment is required for Cryptococcus meningitis

A

Seen in HIV patients
Give IV Amphotericin B/Flucytosine and fluconazole
Creates a very high pressure in CSF so must do regular daily LPs to relieve pressure

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29
Q

Where is Neisseria meningitides usually found

A

Found in the throats of healthy carriers

30
Q

How does neisseira meningitides reach the brain

A

Probably gain access to the meninges through the bloodstream.
The bacteria may be found in leukocytes in CSF

31
Q

What causes the effect in meningococcal meningitis

A

The endotoxin released by Neisseria meningitides

32
Q

Where is H influenza usually found

A

It is part of normal throat microbiota

33
Q

What does H influenza need in order to grow

A

Blood factors

Therefore need to be cultured on chocolate agar

34
Q

Where is strep pneumoniae usually found

A

The nasopharynx

35
Q

Who is most susceptible to strep pneumonia meningitis

A

Hospitalized patients, patients with CSF skull fractures, diabetics/ alcoholics and young children
May be linked to CNS implants like cochlear
Some occur secondary to pneumonia

36
Q

Which group will struggle to fight off encapsulated organisms

A

Those without a spleen

Puts them at higher risk

37
Q

The pneumococcal vaccine also protects against meningitis - true or false

A

True

38
Q

What antibiotic is needed to treat listeria

A

IV ampicillin or amoxicillin

39
Q

What type of bacteria is listeria

A

Gram positive bacilli

40
Q

What are the signs of TB meningitis

A

Usually a reactivation of the infection in the elderly
Will have been non-specifically ill for weeks
May have had previous Tb in CXR

41
Q

How do you treat TB meningitis

A

Isoniazid and rifampicin are the key ones

Also add pyrazinamide and ethambutol

42
Q

What investigations would you do for suspected meningitis

A

Bloods - cultures, FBC, U&E< LF, PCR, serology
Throat swab - culture
LP - unless signs of sepsis
Can move onto viral PCR if that is the likely cause

43
Q

What tests can be done on a CSF sample in suspected meningitis

A

Haematology - cell count and differential
Microbiology - gram stain (done immediately) and cultures (takes several days)
Chemistry - glucose and protein

44
Q

How will glucose change in the CSF of someone with meningitis

A

It will be lower than usual

This is because the bacteria present will consume glucose

45
Q

All bacterial meningitis will gave a positive culture - true or false

A

FALSE
around 10-15% are culture negative
Also even short duration of treatment can turn samples negative (e.g. if LP was delayed but antibiotics were started)

46
Q

Which viruses commonly cause meningitis

A

Enterovirus - in autumn/summer and associated with GI symptoms
HSV1 and 2 - will have cold sores

In immunocompromised can be EBV or CMV

47
Q

Describe the CSF findings in a viral meningitis

A

Predominantly lymphocytes
Negative gram stain
Normal protein (may be slight increase)
Normal glucose

48
Q

Describe the CSF findings in a bacterial meningitis

A

Predominantly polymorphs
Positive gram stain
High protein
Lower glucose - less than 70% of BG

49
Q

Describe the CSF findings in a tuberculosis meningitis

A

Predominantly polymorphs
Positive or negative gram stain
Very high protein
Lower glucose - less than 60% of BG

50
Q

What is aseptic meningitis

A

Means a non-pyogenic bacterial meningitis - doesn’t produce pus
Will have normal glucose and protein and less WBC

51
Q

What are the indications for hospital admission in suspected menigitis

A

Signs of meningeal irritation An impaired conscious level
A petechial rash
Febrile or unwell and have had a recent fit
Any illness, especially headache in those who have come into close contacts with meningococcal infection

52
Q

What is the immediate management of suspected meningitis on admission

A

Take blood for culture and coagulation screen
Start empirical treatment
Take throat swab
Disrupt and swab any skin lesions

53
Q

When should you do a CT before an LP

A 
Immunocompromised 
History of CNS disease 
New onset seizure 
Papilloedema - or other signs of raised ICP 
Abnormal level of consciousness 
Focal neurological deficit
54
Q

What are the indications for LP

A

ALL adults with suspected meningitis require one

UNLESS there is a clear contraindication or there’s a confident clinical diagnosis

55
Q

Antibiotics should be started immediately, before investigations have come back (e.g. LP) - true or false

A

In suspected meningitis it is TRUE

56
Q

Why are steroids given in meningitis

A

It reduced unfavourable outcomes and mortality

Give alongside the doses of antibiotics

57
Q

When would you not give steroids in meningitis

A

Post-surgical meningitis, severe immunocompromise, meningococcal or septic shock or those hypersensitive to steroids

58
Q

How can you prevent secondary cases of meningitis

A

Report all clinically suspected cases to public health ASAP
GPs can contact close contacts to allow implementation of prophylaxis
Label those at risk as higher risk persists for 6 months

59
Q

What prophylaxis is available for those who have been in contact with

A

600mg rifampicin every 12 hours for 4 doses
Lower dose for young kids - 10mg/kg
OR
500mg ciprofloxacin single dose in adults

60
Q

What vaccines are available for meningitis

A

Neisseria meningitidis - groups A,C,W,Y
H. influenza - HiB
Strep pneumo - pneumococcal vaccine

61
Q

What is a normal protein ratio in CSF

A

<0.4

62
Q

What is a normal glucose ratio in CSF

A

> 0.6 glucose (CSF:blood),

Usually around 60-70% of blood glucose

63
Q

What are the normal CSF white and red cell counts

A

No red cells and no more than 5 white cells per mm3

64
Q

What does normal CSF look like

A

Clear and colourless with no blood or neutrophils

65
Q

What is meant by a blanching rash

A

Disappears when pressure is applied

66
Q

Is it safe to do an LP in a patient without a CT first

A

Nope
Need to look for signs of raised ICP, focal deficits or seizure
If CT is abnormal or symptoms present then not safe due to herniation risk

67
Q

How do Neisseria meningitidis appear on staining

A

Gram-negative diplococci

68
Q

What prophylaxis is given to those who come into contact with meningitis

A

Ciprofloxacin

69
Q

How can you treat HSV encephalitis

A

IV aciclovir

70
Q

How do you treat encephalitis

A

IV Ceftriaxone and dexamethasone
Amoxicillin for listeria cover
Acyclovir if HSV risk

71
Q

Middle ear infections can lead to encephalitis - true or false

A

True

Recurrent infections increase risk as it can spread to brain

72
Q

Which organisms can cause brain abscesses

A
  • strep pneumoniae
  • Bacteroides
  • staph

Neurology (18 decks)

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