Bacterial CNS Infection

Question 2

gram-negative diplococci found in the upper respiratory tract

Answer 2

neisseria meningitidis

Question 3

gram-negative rods found in the GI tract

Answer 3

escherichia coli (usually in young, elderly, and immunosuppressed)

Question 4

gram-negative coccobacilli found in the upper respiratory tract

Answer 4

haemophilus influenzae (not seen very much because of effective vaccine)

Question 5

gram-positive cocci in short chains found in GI tract and lower female genital tract

Answer 5

streptococcus agalactiae (GBS)

Question 6

what type of hemolysis is expected with Group B Strep?

Answer 6

subtle beta hemolysis

Question 7

gram-positive cocci in short chains found in the upper respiratory tract

Answer 7

streptococcus pneumoniae (can see “halo” of capsule, can differentiate based on positive P disk–optichin and alpha-hemolysis)

Question 8

gram positive cocci in clusters found in skin, nares

Answer 8

staphylococcus aureus (also beta hemolytic, catalase +, coagulase +)

Question 9

gram-positive facultative intracellular rods found in GI tract

Answer 9

listeria monocytogenes (can cause meningitis in children)

Question 10

acid-fast bacillus in lower respiratory tract

Answer 10

mycobacterium tuberculosis

Question 11

spirochete that disseminates from the urogenital tract

Answer 11

treponema pallidum (Syphilis)

Question 12

spirochete transmitted by black legged ticks

Answer 12

borrelia burgdorferi (Lyme disease)

Question 13

what are the 3 most likely causes of bacterial meningitis in newborns?

Answer 13

1) GBS, 2) E. Coli, 3) L. monocytogenes

Question 14

what are the 2 most likely causes of bacterial meningitis in people >3mo old?

Answer 14

1) Strep pneumoniae, 2) N. meningitidis

Question 15

what is opisthotonos, and what is it a sign of?

Answer 15

rigidity with arched back and head thrown backwards, seen in infants, sign of meningitis

Question 16

where is the greatest risk of getting meningitis?

Answer 16

the meningitis belt in central Africa (meningococcal form)

Question 17

when and why is meningococcal meningitis so common in central Africa?

Answer 17

dry season (cold nights, wind-blown dust) irritates the nasal and respiratory passages, increasing the risk of invasive disease in those already colonized by N. meningitidis

Question 18

when were meningococcal polysaccharide vaccines first developed?

Answer 18

1969 by military doctors, basis of current bivalent and quadrivalent

Question 19

what is different about the meningococcal vaccine that was developed in the last 10 years?

Answer 19

it is a conjugate vaccine that protects against 4 of the 5 major disease-causing serogroups (A,C,Y, and W-135)

Question 20

what differs among the various meningococcal serotypes?

Answer 20

the polysaccharide capsule

Question 21

which meningococcal serotype is not covered by the vaccine, and why?

Answer 21

the type B capsule, because it is made of carbohydrates similar to those found in the fetal brain (molecular mimicry - poor immunogen, concern for cross-reaction)

Question 22

what distinguishes N. meningitidis from N. gonorrhea?

Answer 22

CAPSULE (otherwise looks very similar)

Question 23

describe the pathogenesis of N. meningitidis?

Answer 23

1) adheres to non-ciliated epithelium, 2) internalized, 3) replicated intracellularly, 4) trancytosed thru BL tissue, 5) disseminates into blood

Question 24

what type of skin lesions are seen with invasive meningococcal infections?

Answer 24

hemorrhagic skin lesions that are macular or non-blanching petechiae

Question 25

how do meningococci invade the CNS?

Answer 25

high blood concentrations, bacteria cross BBB of meningeal blood vessels and enter subarachnoid space, then can enter lateral ventricles through choroid plexus –> proliferation and super high concentration in CSF

Question 26

Brudzinski’s sign

Answer 26

severe neck stiffness causes a patient’s hips and knees to flex when neck is lifted off table (flexed) – sign of meningitis

Question 27

Kernig’s sign

Answer 27

severe hamstring stiffness causes inability to straighten leg when hip is flexed to 90 degrees

Question 28

describe the typical CNS profile for meningococcal meningitis

Answer 28

CSF is cloudy due to WBCs and bacteria, WBC highly elevated (1000-5000) with PMN predominance, decreased glucose (less than 1/2 serum level), elevated protein (>100)

Question 29

what is a common virulence factor found in bacteria (and fungi) that cause meningitis?

Answer 29

most of them have polysaccharide capsules (N. meningitidis, E. coli, H. influenzae, S. pneumoniae, GBS, S. aureus, c. neoformans

Question 30

name 4 non-encapsulated bacteria that infect the CNS

Answer 30

listeria monocytogenes, mycobacterium TB, treponema pallidum, borrelia burgdorferi

Question 31

what 3 virulence mechanisms enable listeria to invade the CNS?

Answer 31

transport inside monocytes (Trojan Horse), direct invasion of endothelial cells, invasion of cranial nerves (by bacteria in oral macrophages) and retrograde movement into CNS

Question 32

what virulence factor enables TB to get into the CNS?

Answer 32

it is maintained inside macrophages

Question 33

what is unique about T. pallidum and B. burgdorferi that allows them to enter the CNS?

Answer 33

they are spirochetes whose corkscrew motility allows them to squeeze through the epithelium of the BBB

Question 34

in what ways does listeria meningitis present atypically?

Answer 34

longer course, encephalitis-like symptoms, often no bacterial meningitis CSF findings, CSF gram stain shows no bacteria

Question 35

describe TB meningitis

Answer 35

TB forms small foci in the meninges and brain parenchyma that can rupture and lead to inflammatory meningitis; TB invades microglia cells and can become walled off in spinal cord (Pott’s disease)