CNS Infections

Question 1

Meningitis

Answer 1

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

Question 2

Names for viral versus bacterial meningitis

Answer 2

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

Question 3

Bacterial Meningitis

Answer 3

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

Question 4

Haemophilus type meningitis

Answer 4

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

Question 5

Meningismis

Answer 5

Stiff neck

Photophobia

Question 6

Causes of meningitis

Answer 6

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

Question 7

Viral meningitis

Answer 7

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

Question 8

Some common bacterial meningitis agents

Answer 8

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

Question 9

Bacterial meningitis agents for those:

Less than 3 months old (4)

Answer 9

Group B strep
Listeria monocytogenes
E. coli
Strep pneumoniae

Question 10

Bacterial meningitis agents for those:

3 months to 18 years (3)

Answer 10

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

Question 11

Bacterial meningitis agents for those:

18 to 50 (3)

Answer 11

S. pneumoniae
N. meningitidis
H. influenzae

Question 12

Bacterial meningitis agents for those:
Over 50 (3)

Answer 12

S. pneumoniae
L. monocytogenes
Gram negative bacilli

Question 13

Lumbar puncture

Answer 13

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

Question 14

Typical findings in meningitis: bacterial versus viral

1. Cell types
2. CSF protein level
3. CSF glucose level

Answer 14

1. B: presence of NEUTROPHILS, V: presence of LYMPHOCYTES
2. B: 10X normal, V: 2-3X normal
3. B: very low, V: normal

Question 15

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

Answer 15

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

Question 16

Neisseria meningitidis

Answer 16

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

Question 17

Meningitis common clinical presentations

Answer 17

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

Question 18

Meningococcemia common clinical presentations

Answer 18

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

Question 19

Meningitis transmission

Answer 19

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

Question 20

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

Answer 20

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

Question 21

3 vaccines for N. meningitidis

Answer 21

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

Question 22

Listeria monocytogenes

Answer 22

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

Question 23

Clinical manifestations of Listeria

Answer 23

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

Question 24

What do you use to treat bacterial meningitis?

Answer 24

Vanco and a high dose of a 3rd generation cephalosporin

If they are elderly, add ampicillin

Question 25

Listeriolysin O

Answer 25

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

Question 26

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

Answer 26

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 :(

Question 27

Mental status changes

Answer 27

Seizures, decreased consciousness, confusion | Ex: encephalitis has meningitis symptoms + mental status changes

Question 28

When to think viral CNS infection | CSF exam and clinical presentation

Answer 28

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

Question 29

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

Answer 29

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

Question 30

Herpes simplex virus | family, nucleic acid, types and diseases, outbreaks?, mortality, pathogenesis, diagnosis, treatment

Answer 30

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

Question 31

Acyclovir

Answer 31

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

Question 32

Arboviruses

Answer 32

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

Question 33

Vector

Answer 33

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

Question 34

4 Arboviruses that cause encephalitis

Answer 34

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

Question 35

Reservoir

Answer 35

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

Question 36

Epidemic (or urban) cycle

Answer 36

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

Question 37

Enzootic cycle (sylvatic or jungle cycle)

Answer 37

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

Question 38

Epizootic cycle (rural cycle)

Answer 38

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

Question 39

How does Eastern Encephalitis Virus get into humans?

Answer 39

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

Question 40

Rabies virus encephalitis | (family, nucleic acid, enveloped?, where globally, transmission, symptoms, diagnosis, treatment, prevention

Answer 40

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

Question 41

Meningitis vs encephalitis

Answer 41

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