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MICRO ADYA > Microbiology 5 - CNS infections and meningitis > Flashcards

Microbiology 5 - CNS infections and meningitis Flashcards

1
Q

Which antibiotic should be used first line in meningitis?

A

Ceftriaxone

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2
Q

Is listeria meningitis is suspected, what antibiotic therapy should be used?

A

Ceftriaxone plus amoxicillin

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3
Q

Which pathogen is most likely to be the cause in myelitis?

A

Poliovirus

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4
Q

What is myelitis?

A

Inflammation of the spinal cord

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5
Q

Recall the 3 most likely causative organisms in acute meningitis, and the most susceptible demographic of patient to each

A

N. meningitidis = young
S. pneumoniae = elderly (so vaccine at 65 years)
H. influenzae = those who haven’t had HiB vaccine

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6
Q

What is the most commonn cause of meningitis in neonates?

A

Group B strep

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7
Q

What is the most likely causative organism in chronic meningitis?

A

TB

(or cryptococcus according to path guide)

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8
Q

What is the most likely causative organism in aseptic meningitis?

A

Coxsackie virus

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9
Q

Describe the rash produced by meningococcal meningitis

A

Non-blanching purpuric rash

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10
Q

What is the most likely viral cause of encephalitis in the UK and worldwide?

A

UK: HSV 1
Worldwide: WNV

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11
Q

Recall 3 possible routes of infection that may cause a brain abscess

A

Direct expansion from

  • otitis media
  • mastoiditis
  • paranasal sinusitis
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12
Q

What is the most common type of spinal vertebral infection?

A

Pyogenic vertebral osteomyelitis

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13
Q

What is the most common cause of pyogenic vertebral osteomyelitis?

A

Infective endocarditis - staph/ strep can be ‘flicked off’ the valve

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14
Q

What is the first investigation to do in suspected meningitis?

A

Blood cultures

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15
Q

Recall the stains used in CSF analysis to look for a) bacteria b) TB and c) fungi

A

a) gram stain
b) auramine stain
c) India ink

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16
Q

If “alpha haemolytic diplococci” are found in CSF, what is the pathogen causing meningitis?

A

Streptococcus pneumoniae

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17
Q

What is the normal range for CSF protein?

A

0.15-0.4

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18
Q

What is the appearance of CSF in purulent vs aseptic vs TB meningitis?

A

Purulent: turbid
Aseptic/ TB: slightly turbid or clear

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19
Q

What type of cell is elevated in the CSF in purulent vs aseptic vs TB meningitis?

A

Purulent: polymorphs
Aseptic/ TB: lymphocytes

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20
Q

In which type of meningitis will gram stain antigen tests be positive?

A

Purulent meningitis

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21
Q

Which type of meningitis produces the most protein in CSF?

A

TB meningitis

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22
Q

What is the empirical therapy for meningitis?

A

Ceftriaxone 2g IV bd
Add amoxicillin if >50 or immunocompromised

ALSO GIVE STEROIDS (DEXAMETHASONE) (as long as >1 month old and NOT MENINCOCCOCAL)

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23
Q

What are the routes of infection into the CNS and which is the most common?

A

Haematogenous spread (e.g. pneumococcus, meningococcus, herpes)

Direct implantation (e.g. trauma)

Local extension (e.g. from the ear)

PNS to CNS (e.g. rabies)

*haematogenous is the most common

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24
Q

Which organisms cause aspetic meningitis?

A

Herpes

Enteroviruses

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25
Q

3 big causes of acute meningitis

A

Neisseria

Haemophilus

Strep Pneumoniea

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26
Q

Incidence of rash with N. Meningitidis

A

A nonblanching rash develops in 80% of children

A maculopapular rash remain in 13% of children and no rash in 7%

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27
Q

How quickly do you need to give antibiotics for N. Meningitidis infection?

A

Within 1 hour

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28
Q

N Meningiidtis Gram stain

A

Gram negative, non haemolytic, cofffee bean shaped diplococcus

29
Q

Age distribution of Strep Pneumoniea

A

Bimodal

a) children/young people
b) elderly

30
Q

S. Pneumoniea LP gram stain and blood agar plate

A

Gram positive diplococci with some erythrocytes

Blood agar plate: partial alpha haemolysis

31
Q

Listeria gram stain

A

Gram positive rods

32
Q

What organism commonly causes meningoencephalitis?

A

Listeria monocytogenes

33
Q

Which age groups does E. Coli meningitis affect?

A

Bimodal age distribution

a) neonates
b) elderly/immunocompromised - from UTIs

34
Q

Which organisms cause meningitis in neonates?

A

Group B Strep

E Coli

Listeria

(GEL)

35
Q

Why is LP contraindicated in meningococcal septicaemia?

A

Coagulopathy

can lead to paresis from LP site downwards

36
Q

Which organisms cause chronic meningitis?

A

TB

Cryptococcus- only seen in HIV

Spirochetes

37
Q

Which group of patients does TB meningitis affect?

A

Mainly immunocompromised

38
Q

TB: LP gram stain and MRI findings

A

LP gram stain: show up using Ziehl Neilson stain - cuboidal structures that appear red against blue stain

MRI: leptomeningeal enhancement

39
Q

Complications of TB meningitis

A

Abscesses

Granulomas

Cerebreitis (i.e. inflammation of the cerebrum itself)

40
Q

Cryptococcus meningitis - LP findings - gram stain and opening pressure

A

LP findings: using INDIAN INK STAIN- appears like an orbit. Yeast in the middle with a capsule around the outside

Opening pressure - HIGH

41
Q

Tx of cryptococcal meningtis

A

Amphoterecin

42
Q

Which is the most common infection of the CNS?

A

Aseptic meningitis - i.e. viral

43
Q

Which organisms commonly cause aseptic meningitis?

A

Enterovirus: Cocksackie B and echoviruses

HSV 1 and 2

44
Q

WHich age group does aseptic meningitis tend to affect?

A

Young children <1 year

45
Q

How do you manage aseptic meningitis?

A

It is acute and self limiting. resolves within a few weeks

Give supportive treatment like analgesia, anti-emetics etc.

46
Q

Most common causative organism of encephalitis in the UK

A

Herpes Simplex Virus

47
Q

Another viral cause of encephalitis that is becoming more common internationally

A

West Nile Virus- becoming leading cause internationally

Spreading west towards UK

48
Q

Bacterial causes of encephalitis

A

Listeria monocytogenes

49
Q

Parasitic causes of encephalitis

A

Toxoplasmosis

An obligate intracellular protozoal parasite, Toxoplasma gondii

Via the oral, transplacental route or organ transplantation

Causes severe infection in immunocompromised patients

50
Q

AMoebic causes of encephalitis

A

Naegleria fowleri

Habitat- warm water

Acanthamoeba species, and Balamuthia mandrillaris

^can cause brain abscesses, aseptic or chornic meningitis

51
Q

What differentiates meningitis and encephalitis?

A

The disturbance of cognitive function (ENCEPHAITIS) is what differentiates meningitis to encephalitis

52
Q

Difference between management of herpes meningitis and herpes encephalitis:

A

Herpes meningitis does NOT need therapy

BUT herpes encephalitis is a MEDICAL EMERGENCY

53
Q

2 causative organisms of brain abscesses

A
  • Streptococci (both aerobic and anaerobic)
  • Staphylococci
  • Others:
    • Gram-negative organisms (particularly in neonates)
    • Mycobacterium tuberculosis
    • Fungi
    • Parasites
    • Actinomyces and Nocardia species
54
Q

Cerebral abscess: MRI finding

A

Ring enhancing lesion

55
Q

Which routes of bacterial entry enable spread to become brain abscess?

A
  1. Direct extension: from otitis media or sinusitis or mastoiditis
  2. Haematogenous- especially from endocarditis, caused by Staph and Strep
56
Q

Why are brain abscesses dangerous?

A

They cause death through compression of structures

57
Q

Osteomyelitis vs myelits

A

Osteomyelitis: Inflaqmmation of the vertebrae

Myelitis: inflammation of the spinal cord

58
Q

Osteomyelitis: common organisms, route of entry, age distribution,

A

a) most common organism: Staph auerus
b) routes of spread:
1) Derives from central site of infection:
e. g. endocarditis flicking off emboli
2) Direct open spinal trauma:

from infections in adjacent structures

3) Haematogenous spread of bacteria:particularly from S. pneumoniae

to a vertebra

c) risk factors

  • Advanced age
  • Can occur in pregnant women
  • IVDU
  • Long-term systemic steroids
  • Diabetes mellitus
  • Organ transplantation
  • Malnutrition
  • Cancer
  • LPs can also cause this
59
Q

What organism commonly causes myelitis?

A

Poliovirus

60
Q

CSF results table

A
61
Q

CT vs MRI for detecting neurological lesions

A

MRI is better for parenchymal detection

but CT is obviously cheaper

62
Q

Generic therapy for meningitis

A

IV ceftriaxone

If >50 or immunocompromised- add amoxicillin

63
Q

Generic therapy for meningo-encephalitis

A

IV ceftriaxone + IV aciclovir

Add amoxicillin if >50 or immunocompromised

64
Q

When do you isolate patients with meningitis? And what do you give to contacts?

A

Isolate only if menigococcal- not if aseptic

Need to give ciprofloxacin to contacts

65
Q

Summary table of specific therapy for meningitis

A
66
Q

What type of organism is Haemophilus influenzae

A

Gram negative

Non-spore forming

Cocobacillary rods

Encapsulated

Immotile

67
Q
A
68
Q

Where can brain abscess spread from?

A

Otitis media

haematogenous spread

69
Q

Normal blood csf glucose

A

2.2-2.3 (60% of blood level)

MICRO ADYA (22 decks)

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