Chapter 16 Flashcards
What must pathogens cross to cause encephalitis?
Frrom blood over the blood brain barrier
What must pathogens cross to cause meningitis?
From blood to the cerebrospinal fluid
How can microbes cross the BBB?
Growing across, infecting the cells that compromise the barrier
Being passively transported across in intracellular vacuoles
Being carried across by infected white blood cells
Moving through the interstitial space between cells
What are the cell, protein, glucose levels in a normal body?
0-5 cells/ml
15-45 mg protein/dL
45-85 mg glucose/dL
What are the cell, protein, glucose levels in septic meningitis (caused by bacteria)?
200-20,000 cells/ml (mostly neutrophils) High protein (>100) due to bacterial protein
What are the cell, protein, glucose levels in aseptic meningitis or meningoencephalitis?
100-1000 cells/ml (mainly mononuclear
Moderately high protein (50-100) because no bacteria
Normal glucose because viruses don’t metabolize
What causes bacterial meningitis (the more severe, less common meningitis)?
Neisseria meningitidis, streptococcus pneumonia, H. influenzae (before vaccination)
What are the virulence factors needed to cause bacterial meningitis?
Capsule (to prevent phagocytosis by blood complement system)
IgA protease
Pili, endotoxin and outer membrane proteins (N. meningitidis, H. influenzae) also help
Does gram positive or gram negative produce endotoxin?
Gram negative does
What pathogens cause bacterial meningitis in neonates (
Gram negative bacilli (E. coli, Klebsiella, Enterobacter)
Strep. agalactiae, Listeria monocytogenes
Has less well developed BBB
What pathogens cause bacterial meningitis in infants (
Strep. agalactiae, E.coli, H. influenzae, Strep. pneumoniae, N. meningitidis
Less well developed BBB
What pathogens cause bacterial meningitis in children and adults?
Strep. pneumoniae, neisseria meningitidis
Fully developed BBB
What pathogens cause bacterial meningitis in the elderly (>65 years)?
Strep. pneumoniae, N. meningitidis, Listeria monocytogenes, Aerobic gram negative bacilli
BBB starts disintegrating
How much of the population is a carrier for Neisseria meningitidis?
20% (higher rates seen in epidemics)
What causes meningococcal meningitis?
Neisseria meningitidis (looks like N. gonorrhea)
What are the virulence factors of Neisseria meningitidis?
Pili for attachment to the epithelium of the nasopharynx
How does neisseria meningitidis invade the blood and meninges?
Not well understood.
Individuals with C5-C9 complement deficiency are more susceptible.
Young children who have lost maternal antibodies and those who have never encountered the infecting serotype are at the greatest risk
What protects us from invasion of the blood and meninges?
Presence of antibodies to capsular antigens.
How is neisseria meningitidis transmitted?
Droplets, overcrowding and confinement (prisons, dorms, military barracks)
What is the peak time of year for neisseria meningitidis?
Winter/ early spring when carrier rates are 60-80%
What is the clinical manifestation of meningococcal meningitis?
1-3 days after infection, sudden onset of headache, sore throat, drowsiness, stiff neck, hemorrhagic skin rash (indicates septicemia)
100% mortality untreated, 10% mortality if treated
How can you prevent meningococcal meningitis?
Using a vaccine (routine childhood vaccination)
Polysaccharide for young children
Conjugate for >11 years
How is meningococcal meningitidis diagnosed?
Essential to know whether it is viral or bacterial. Gram stain of CSF, culture and white cell counts
What is haemophilus meningitis caused by?
Haemophilus infulenzae B (serotype based on capsule) fastidious
Resident of RT in infants and children and maternal antibodies protect the infant until 3-4 months when they wane
Window of susceptibility before developing its own antibodies
What is the clinical manifestation of haemophilus meningitis?
5-6 days after infection hearing loss, delayed language development, mental retardation
Less fatal than meningococcal and pneumococcal
How can we prevent haemophilus meningitis?
With the HiB vaccine after 2 months
What causes pneumococcal meningitis?
Streptococcous pneumoniae
Encapsulated
Carried in the throats of many healthy people, rarely invades blood or meninges
Highest mortality rate
What can make a person susceptible to pneumococcal meningitis?
Low levels of capsular antibodies, specific, >85 capsule types
How can we prevent pneumococcal meningitis?
Heptavalent protein conjugate for 2-23 months and immunocompromised
23-valent for >5 years (could cause hypersensitivity reaction in babies)
What typically causes viral meningitis?
Enteroviruses
What is the clinical manifestation of viral meningitis?
Most common type, milder than bacterial (headache, fever, photophobia)
Complete recovery is typical
How do you diagnose viral meningitis?
Difficult to isolate virus from CSF so diagnosis is done with viral genome detection (PCR)
What is encephalitis?
Inflammation of the brain parenchyma, usually viral
Cerebral dysfunction is typical (abnormal behaviour, seizures, nausea, vomiting, fever)
HSV-2 most common cause
How does HSV encephalitis clinically manifest in neonates?
Passage down the birth canal of a female shedding HSV-2
How does HSV encephalitis clinically manifest in older children and adults?
HSV-1 viral reactivation in nerves in skull (trigeminal ganglia) and the infection spreading back to the temporal lobe of brain.
70% fatality if not treated
How is HSV encephalitis treated?
Antiviral therapy for 21 days
What are the symptoms of poliovirus encephalitis?
1-4 days of fever, sore throat, malaise
Effect of motor neurons is paralysis
Formerly the most common cause of encephalitis
What is the only disease that has been eradicated from earth?
Smallpox, polio is likely to be next
How can we prevent poliovirus encephalitis?
Using the inactivated vaccine or oral vaccine
Who carries West Nile Virus?
Birds and culcine mosquitoes with humans and horses being incidental hosts
From Africa, Middle East spread to NYC 1999 by migrating birds
How is West Nile Virus diagnosed?
RNA detection of West Nile Virus or IgM antibodies in sera/CSF
How can we prevent West Nile virus?
No vaccine, only mosquito control
What neurologic diseases may have a viral origin?
MS, Parkinsons, schizophrenia and senile dementia
How did Alexander the Great die?
West Nile virus causing enephalitis
