33a - Bacterial Meningitis

Question 1

What are CSF finidngs in bacterial meningitis?

Answer 1

high protein, low glucose, high WBC, cloudy color

Question 2

Organisms most likely to cause bacterial meningitis in birth-3months?

Answer 2

Group B strep (agalactiae)
Gram neg enteric bacilli
Listeria monocytogenes

Question 3

Organisms most likely to cause bacterial meningitis in 3months-2years?

Answer 3

strep pneumo
neisseria meningitides
haemophilus influenzae type b

Question 4

Organisms most likely to cause bacterial meningitis in 2 yrs - 18yrs?

Answer 4

neisseria meningitides

streptococcus pneumoniae

Question 5

Organisms most likely to cause bacterial meningitis in immunocompromised?

Answer 5

staph
gram negative enteric bacilli
pseudomonas aruginosa

Question 6

What is group A strep?

Answer 6

strep pyogenes.

normal inhabitant of upper respiratory tract in 15% of people bu tcause numerous local and systemic diseases.

Question 7

Most common cause of otitis media in infants and children?

Answer 7

strep pneumoniae

Question 8

Where does strep pneumo colonize?

Answer 8

it tightly adheres to nasopharyngeal epithelium then spreads to lower respiratory tract or blood

Question 9

What are the virulence vactors of strep pneumo

Answer 9

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

Question 10

What are the preventative measures for strep pneumo?

Answer 10

pnuemovax and prevnar.

Question 11

What is the difference between pneumovax and prevnar

Answer 11

pneumovax - multivalent (non-conjugated)

prevnar - heptavalent (memory response), potentiat to reduce infant pneumococcal meningitis by 85% (expensive)

Question 12

Characteristics of Neisseria miningitidis

Answer 12

gram neg, nonmotile diplococci, prominent antiphagocytic polysaccharide capsule.

Question 13

Where do Neisseria meningitidis infections typically occur?

Answer 13

crowded living conditions. AND predominantly Africa during dry seasons

Question 14

What is clinical presentation of neisseria menigitidis?

Answer 14

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)

Question 15

Virulence factors of neisseria mningitidis?

Answer 15

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

Question 16

What is only known resevoir of neisseria meningitidis?

Answer 16

human nasopharynx. Spread via respiratory droplets.

Question 17

How does neisseiria meningitidis infect?

Answer 17

inhaled. Binds to non-ciliated columnar epithelial cells of nasopharynx

Question 18

What is drug of choice for neisseria meningitidis?

Answer 18

penicillin.. If allergic use chloramphenicol or cephalosporin.

Question 19

is there a vaccine for neisseria meningitids?

Answer 19

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

Question 20

How is haemophilus influenczae spread?

Answer 20

inhaled into nasopharynx (more common in <1 yr olds)

Question 21

What is most important serotype of haemophilus influenzae?

Answer 21

serotype b (Hib)

Question 22

What are virulence factors of h. influenzae?

Answer 22

capsule (main thing)

Question 23

Is there a vaccine for h. influenzae?

Answer 23

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.

Question 24

Characteristics of Listeria monocytogenes?

Answer 24

gram+ rod. facultative intracellular parasite.

Question 25

clinical presentation of listeria monocytogenes infection?

Answer 25

mild flu-like prodrome, less commonly diarrhea and abdominal discomfort.

Question 26

Reservoir of listeria monocytogenes?

Answer 26

widespread in nature. Chickens and sheep.
Human intestinal and vaginal. Raw dairy, meat and veggies.
Grows in cold storage but killed by pasteurization.

Question 27

How does listeria monocytogenes infect?

Answer 27

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

Question 28

What is replication cycle of listeria monocytogenes?

Answer 28

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.