33a - Bacterial Meningitis Flashcards
What are CSF finidngs in bacterial meningitis?
high protein, low glucose, high WBC, cloudy color
Organisms most likely to cause bacterial meningitis in birth-3months?
Group B strep (agalactiae)
Gram neg enteric bacilli
Listeria monocytogenes
Organisms most likely to cause bacterial meningitis in 3months-2years?
strep pneumo
neisseria meningitides
haemophilus influenzae type b
Organisms most likely to cause bacterial meningitis in 2 yrs - 18yrs?
neisseria meningitides
streptococcus pneumoniae
Organisms most likely to cause bacterial meningitis in immunocompromised?
staph
gram negative enteric bacilli
pseudomonas aruginosa
What is group A strep?
strep pyogenes.
normal inhabitant of upper respiratory tract in 15% of people bu tcause numerous local and systemic diseases.
Most common cause of otitis media in infants and children?
strep pneumoniae
Where does strep pneumo colonize?
it tightly adheres to nasopharyngeal epithelium then spreads to lower respiratory tract or blood
What are the virulence vactors of strep pneumo
capsule - prevents phagocytosis
pili - attachment to epithelial cells in URT, also virualnce transfer
cell wall compoenents (inflammatory)
Choline binding proteins (CBP) - adhesins to epithelial surface carbohydrates. Help cross BBB in meningitis.
Hemolysisn/Pneumolysis -lysis of cells and complement activation
Hydrogen peroxide - damage to hast cells and bactericidal to S. aureus and competitors
Neuraminidase and IgA protease - invasion of host tissue and destruction of mucosal IgA
What are the preventative measures for strep pneumo?
pnuemovax and prevnar.
What is the difference between pneumovax and prevnar
pneumovax - multivalent (non-conjugated)
prevnar - heptavalent (memory response), potentiat to reduce infant pneumococcal meningitis by 85% (expensive)
Characteristics of Neisseria miningitidis
gram neg, nonmotile diplococci, prominent antiphagocytic polysaccharide capsule.
Where do Neisseria meningitidis infections typically occur?
crowded living conditions. AND predominantly Africa during dry seasons
What is clinical presentation of neisseria menigitidis?
fulminant meningococcemia in 15% (mortality)
abrupt high fever, stiff neck , chlls, myalgias, N/V, headache.
Delirium and restlessness within hours.
Sudden appearance of petechial and purpuric skin lesions.
Pulmonary insufficiency within hours. (death in 24 hours even with treatment sometimes)
Virulence factors of neisseria mningitidis?
major toxin is LOS (lipooligosaccharide endotoxin)
polysaccharide capsule
pili to bind to nasopharynx epithelium.
High frequency of genetic variation: Phases variation (turning off capsule genes to invade bloodstream, then turning them back on)
Antigenic variation
What is only known resevoir of neisseria meningitidis?
human nasopharynx. Spread via respiratory droplets.
How does neisseiria meningitidis infect?
inhaled. Binds to non-ciliated columnar epithelial cells of nasopharynx
What is drug of choice for neisseria meningitidis?
penicillin.. If allergic use chloramphenicol or cephalosporin.
is there a vaccine for neisseria meningitids?
menomune - unconjugated so no memory. given only to high risk individuals and military personnel.
Menactra - conjugate (memory). ages 11-55, recommended for all 11-12 year olds.
No vaccine for serogroup B
How is haemophilus influenczae spread?
inhaled into nasopharynx (more common in <1 yr olds)
What is most important serotype of haemophilus influenzae?
serotype b (Hib)
What are virulence factors of h. influenzae?
capsule (main thing)
Is there a vaccine for h. influenzae?
yes. Hib. given to children between 2 and 15 months. Used to be most common cause of bacterial meningitis in young children but vaccine has stopped it.
Characteristics of Listeria monocytogenes?
gram+ rod. facultative intracellular parasite.
clinical presentation of listeria monocytogenes infection?
mild flu-like prodrome, less commonly diarrhea and abdominal discomfort.
Reservoir of listeria monocytogenes?
widespread in nature. Chickens and sheep.
Human intestinal and vaginal. Raw dairy, meat and veggies.
Grows in cold storage but killed by pasteurization.
How does listeria monocytogenes infect?
attches to epithelial cells and macros.
Endocytosis by internalin which binds to E-cadherin.
Then direct cell-to-cell spread so humoral immunity never develops
What is replication cycle of listeria monocytogenes?
endocytosis by internalin binding to E-cadherin.
2 - release from phagolysosome by listeriolysin O
3 - f-Actin based motility
4 - invasion of adjacent cell
5 - bacterial replication
6 - cell death.
