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Clinical Microbiology > CNS Infections > Flashcards

CNS Infections Flashcards

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1
Q

Meningitis

A

An infection which causes inflammation of the membranes covering the brain and spinal chord

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2
Q

Names for viral versus bacterial meningitis

A

Viral: aseptic meningitis (usually resolve without treatment)
Bacterial: purulent meningitis (very serious, may result in death or brain damage)

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3
Q

Bacterial Meningitis

A

Potentially life threatening disease
Fever, headache, meningismis and altered mental status in more that 85% of people
Affects all age groups but some are at higher risk
Pneumococcal meningitis most common type

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4
Q

Haemophilus type meningitis

A

Incidence declined since 1985 due to the introduction of the Haemophilus influenza b vaccine

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5
Q

Meningismis

A

Stiff neck

Photophobia

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6
Q

Causes of meningitis

A 
Bacterial infections
Viral infections
Fungal infections
Inflammatory diseases
Cancer
Trauma to head or spine
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7
Q

Viral meningitis

A

Generally benign, rarely fatal
Enterovirus is 80% of cases, others can be mumps or EBV
Rare but very serious: HSV
No specific treatment except for HSV/VZV - requires systemic antivirals (acyclovir)
Most clear in 3-8 days

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8
Q

Some common bacterial meningitis agents

A 
S. pneumoniae
N. meningitidis
H. influenzae type B
Listeria monocytogenes (very young and very old)
Group B strep (neonates)
Others
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9
Q

Bacterial meningitis agents for those:

Less than 3 months old (4)

A

Group B strep
Listeria monocytogenes
E. coli
Strep pneumoniae

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10
Q

Bacterial meningitis agents for those:

3 months to 18 years (3)

A

N. meningitidis
S. pneumoniae
H. influenzae (rare)

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11
Q

Bacterial meningitis agents for those:

18 to 50 (3)

A

S. pneumoniae
N. meningitidis
H. influenzae

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12
Q 
Bacterial meningitis agents for those:
Over 50 (3)
A

S. pneumoniae
L. monocytogenes
Gram negative bacilli

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13
Q

Lumbar puncture

A

Collects cerebral spinal fluid to check for the presence of disease or injury
Spinal needle is inserted, usually between the 3rd and 4th lumbar vertebrae in the lower spine
Permits the urgent distinction of bacterial meningitis from viral and examination of the CSF allows precise diagnosis

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14
Q

Typical findings in meningitis: bacterial versus viral

  1. Cell types
  2. CSF protein level
  3. CSF glucose level
A
  1. B: presence of NEUTROPHILS, V: presence of LYMPHOCYTES
  2. B: 10X normal, V: 2-3X normal
  3. B: very low, V: normal
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15
Q

Why is there not that much glucose present in bacterial meningitis CSF?

A

Because there is so much inflammation that you impair sugar transport
NOT that they use it up

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16
Q

Neisseria meningitidis

A

Gram negative
Aerobic diplococcus
Polysaccharide capsule
13 serogroups classified by their capsule (5 disease ones: A, B, C, Y, W-135)
Often appear intracellular on gram stain
Catalase and oxidase +
Will grow on both chocolate and bloodagars

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17
Q

Meningitis common clinical presentations

A 
Fever and headache (flu like symptoms)
Stiff neck
Nausea
Altered mental status
Seizures
Up to 40% fatality even with appropriate treatment
18
Q

Meningococcemia common clinical presentations

A

Rash
Vascular damage
DIC (disseminated intravascular coagulation)
Multi-organ failure
Shock
Death can occur <24 hours
Fatality rate 3-10% even with appropriate treatment

19
Q

Meningitis transmission

A

Humans only
Asymptomatic pharyngeal carriage can occur in 10-30% of the population
Transmission by saliva, most often by aerosol effect (coughing, sneezing), kissing, etc
Over crowding fosters transmission
Incubation period varies between 2-10 days

20
Q

If you see N. meningitis in the lab, should you tell the doctor to treat right away?

A

No! Because 30% of people have it at all times anyways

21
Q

3 vaccines for N. meningitidis

A

Monovalent serogroup C
Quadrivalent serogroups A, C, Y, W-135
Monovalent serogroup B

22
Q

Listeria monocytogenes

A 
Gram positive bacilli
Catalase positive
Tumbling motility at 25degC
Umbrella motility in semi-soft agar
Beta hemolytic
CAMP test +
23
Q

Clinical manifestations of Listeria

A

Meningitis
Abortion (premature delivery of stillborn or acutely ill infant)
Perinatal septicemia (infant often dies within a few minutes of hours, symptoms reflect disturbances of respiratory, circulatory or central nervous system, if infant survives, meningitis common, often fatal or leads to permanent mental deficiency)
Other influenza like illness

24
Q

What do you use to treat bacterial meningitis?

A

Vanco and a high dose of a 3rd generation cephalosporin

If they are elderly, add ampicillin

25
Q

Listeriolysin O

A

Most significant virulence factor
Responsible for beta hemolysis of erythrocytes and destruction of phagocytic cells
Aids in escape from the phagosome
Present in all strains of L. monocytogenes

26
Q

Should you do the lumbar puncture before or after giving antibiotics?

A

Before
Unless there is going to be a delay and you need to get treated asap
If you give antibiotics first you might sterilize the CSF :(

27
Q

Mental status changes

A

Seizures, decreased consciousness, confusion

Ex: encephalitis has meningitis symptoms + mental status changes

28
Q

When to think viral CNS infection

CSF exam and clinical presentation

A

CSF exam: Gram stain negative, lots of lymphocytes, occasionally increased RBCs, high protein, normal glucose
Clinical presentation: usually acute onset, can effect healthy hosts but more likely immunocompromised, frequently occurs as meningoencephalitis

29
Q

Enterovirus
(family, enveloped?, nucleic acid, disease it causes, who is at risk, outbreaks?, clinical symptoms, treatment/vaccine?, diagnosis)

A

Family: picronaviridae
Non-enveloped, + ssRNA
Respiratory virus
Causes 30-50% of viral meningitis (aseptic meningitis)
People at risk: healthy, neonates, immunocompromised
Seasonal outbreaks
Clinically: usually resp symptoms with severe headaches, can last a while but no long term consequences
No treatment or vaccine
Diagnosis: clinical suspicion/epidemiology, CSF profile, PCR
Treatment: pain control, hydration

30
Q

Herpes simplex virus

family, nucleic acid, types and diseases, outbreaks?, mortality, pathogenesis, diagnosis, treatment

A

Family: Herpesviridae
Enveloped dsDNA
HSV-1 (oral) and 2 (genital) but both can cause CNS disease
Most common cause of sporadic viral encephalitis in NA
No seasonal outbreaks
High mortality even with treatment
Pathogenesis: rarely from primary exposure, usually from reactivation (latency in sensory ganglion)
Symptoms: fever, headache, focal symptoms (temporal lobe), seizures/mental status change frequent), long term consequences possible, immundeficiency can lead to fatal dissemination)
Diagnosis: clinical suspicion, MRI, CSF profile, PCR
Treatment: antivirals (acyclovir), no vaccine

31
Q

Acyclovir

A

Can be used to treat herpes
Nucleotide analogue
Gets incorporated and stops DNA elongation process
Its a prologue though and needs to be activated

32
Q

Arboviruses

A

Arthropod-borne viruses
Major vectors: mosquitoes and ticks
Primary symptoms: mostly asymptomatic or non-specific, fever/headache/seizure, usually meningoencephalitis
Incidence and severity varies with virus and host
Long term consequences possible
Seasonal and geographic distribution
Depends on presence of vector and reservoir
Diagnosis: clinical suspicion, CSF protein, PCR, serology
Supportive treatment
Some vaccines (JEV and YFV)
Vector controll efforts and insect repellant stuff

33
Q

Vector

A

Typically a biting insect or tick that transmits a disease or parasite from one animal to another

34
Q

4 Arboviruses that cause encephalitis

A
  1. West Nile virus
  2. Japanese encephalitis virus
  3. Eastern equine encephalitis virus
  4. La Cross virus
35
Q

Reservoir

A

An organism or population that directly or indirectly transmits a pathogen while being virtually immune to its effects

36
Q

Epidemic (or urban) cycle

A

Reservoir is humans - high level of viremia
Mosquitoes transfer between humans
Ex: dengue, yellow fever, chikungunya, etc

37
Q

Enzootic cycle (sylvatic or jungle cycle)

A

Reservoir: vertebrate - harbors a virus with no ill effects
Mosquitoes transfer between animals (like primates) and humans are accidental hosts
No person-to-person spread
Viremia not sufficient in humans to be picked up by the insect vectors

38
Q

Epizootic cycle (rural cycle)

A

Reservoir: wild birds
Virus transmitted between domestic animals and insect vectors
Epidemic outbreaks in the animal
Amplifying host - possible spillover into humans
Ex: JEV, St-Louis, an Western encephalitis virus

39
Q

How does Eastern Encephalitis Virus get into humans?

A

Indirect spillover into humans through a bridge vector
This is an arthropod that acquires virus from an infected wild animal and subsequently transmits the agent to human or secondary host

40
Q

Rabies virus encephalitis

(family, nucleic acid, enveloped?, where globally, transmission, symptoms, diagnosis, treatment, prevention

A

Family: Rhabdoviridae
Large enveloped virus, ssRNA (-)
More common in underdeveloped countries
Universally fatal once you get symptoms
Transmitted through saliva of infected animals (raccoons, bats, foxes, etc)
Infected animals show no fear for humans, act very agitated, scared of water
Neurotropic (affinity for nerve cells/tissue) - ascending
Long incubation period (3 weeks)
Symptoms: fever, agitation, hydrophobia, painful spasms followed by excessive saliva, universally fatal without treatment
Diag: clinical suspicion, PCR and DFA, serology
Treatment: rabies Ig post exposure
Prevention: vaccination

41
Q

Meningitis vs encephalitis

A 
Meningitis = inflammation of meninges (coverings of brain and spinal chord)
Encephalitis = inflammation of brain itself

Clinical Microbiology (25 decks)

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