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Flashcards in export_cns bacteria i Deck (43):
1

Two main categories of CNS infections

Meningitis (affect meninges)
Encephalitis (affect brain parenchyma)

2

What makes up the blood brain barrier (BBB)?

Tight junctions between endothelial cells of cerebral microvasculature, epithelial cells of choroid plexus, and arachnoid cells

3

What does the BBB do?

Separates blood and CSF, isolating the CNS from the rest of the body

4

How do pathogens gain entry into the CNS?

Hematogenous spread from distant site of inoculation or infection (bacteremia)
Spread from adjacent/contiguous site to CNS

Direct inoculation

Neuronal spread

5

What is meningitis?

Inflammation of the meninges and CSF

6

What are the causes of meningitis, and which is the most severe?

Acute pyogenic (bacterial) - most severe
Aseptic (viral)

Chronic (any class of microbe)

7

Increased risk for meningitis

Pneumonia or chronic otitis media (pneumococcal)
URTI (meningococcal)

8

Virulence factors for meningitis

Capsule
Fimbriae

Pili

MOMPs

9

Pathology of meningitis

Inflammatory mediators initiated due to toxins, resulting in edema, increased intracranial pressure, seizures, coma, and DEATH

10

Diagnose meningitis

Almost all patients have two of the following Sx:

Fever

Headache

Stiff neck

Altered mental status

Labs: CSF Gram-stain, cultures, latex agglutination

11

CSF abnormalities in bacterial meningitis

Presence of PMNs
Decreased glucose

Increased protein

Increased pressure

12

CSF abnormalities of viral meningitis/encephalitis

Monocytes and lymphocytes
Normal glucose

Normal/slightly increased protein pressure

13

Treatment of bacterial meningitis

Empirical antibiotic therapy
Using diagnostic tests can help determine most effective drug

14

Bacterial meningitis causative agents

S. pnuemo
N. meningitidis

S. agalactiae

Listeria monocytogenes

H. influenzae

15

S. pneumo features

Gram-positive cocci in chains
Catalase negative

Alpha-hemolytic


Susceptible to optochin and bile

16

What is the most common cause of vaccine-preventable death in the U.S.?

Pneumococcal meningitis

17

Pneumococcal virulence factors

Choline binding proteins
Pneumolysin

IgA protease

Capsule

18

Choline binding proteins

Allows for colonization in the oropharynx

19

Pneumolysin

Inhibits mucociliary clearance
May also interfere with macrophage clearance

20

Pneumococcal meningitis clinical importance

Acute onset
High mortality

Neurological sequela

21

Pneumococcal meningitis recommended therapy

Vancomycin with a cephalosporin
Modify when organism is identified

22

Pneumococcal polysaccharide vaccine (PPV)

Capsular polysaccharide Ag from 23 types of pneumococcus
Does not prevent pneumonia as effectively

23

Who should get the PPV?

Adults > 65 years old
Anyone > 2 years old with increased risk

24

Pneumococcal conjugate vaccine (PCV13)

Pneumococcal capsule (13 serotypes) conjugated to nontoxic diphtheria toxin

25

Who should get the PCV13?

Routine child vaccine
2, 4, 6 months, then booster at 12-15 months

26

N. meningitides features

Gram-negative diplococcus
Oxidase and catalase positive

Oxidizes BOTH glucose and maltose

Fastidious, requiring CO2

27

N. meningitides virulence factors

Capsule
LOS

28

N. meningitides transmission

~10% of population is colonized
Transmission is via aerosolized droplets

29

Which serotypes cause almost all invasive meningococcal disease?

C
B

Y

W-135

A

30

N. meningitides virulence factors

Pilli
Capsule

LOS

31

LOS effects

Inflammation/immune response
Endotoxemia (organ failure)

DIC

32

N. meningitides entry into CNS

BBB weakened
Cross BBB WITHIN neutrophils

33

What is meningococcemia?

Bloodstream infection occurring with or without meningitis

34

Meningococcemia Sx

Fever
Petechial/purpuric rash

Hypotension

Multiorgan failure

35

What causes meningococcal meningitis?

Hematogenous dissemination

36

Diagnose meningococcal meningitis

Gram-stain of CSF and/or blood
Bacteremia

Susceptibility testing

37

Treatment for meningococcal meningitis

Again, start with vancomycin and a cephalosporin until identification has occurred
N. meningitides is usually susceptible to penicillin, so can use this after identification

38

Meningococcal polysaccharide vaccine (MPV)

Tetravalent polysaccharide vaccine against serotypes A, C, Y, and W-135
Protection against B is on the way

39

Who should get the MPV?

Not recommended as routine vaccination, but should be used in high-risk persons
In event of an outbreak

40

What defines a meningococcal outbreak?

3+ cases in < 3 months

41

Meningococcal conjugate vaccine (MCV4)

Tetravalent against A, C, Y, and W-135 (B still on the way)
Conjugated to nontoxic diphtheria toxin subunit

42

Who should get the MCV4?

Anyone 11-55
9 months-55 years that have increased risk factors

43

Differences between MPV and MCV4?

MCV4 illustrates a booster effect, and has a higher IgG response, and a higher affinity Ab response