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Flashcards in Bacterial CNS Deck (47)
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1

4 major causes of bacterial meningitis

Strep pneumo, neisseria meningitidis, H Flu, Listeria monocytogenes

2

CSF in bacterial meningitis usually associated with

large numbers of polys
reduced glucose
elevated protein

3

Streptococci morphology

Gram positive spherical bacteria that occur in pairs

4

strep pneumo

- also known as pneumococcus
- Normal inhabitants of the upper respiratory tract but MOST COMMON cause of bacterial meningitis in US

5

Strep pyogenes

Also known as group A strep, also normal inhabitants of URT

6

Strep Agalactiae

Group B strep

7

Viridans Streptococci

dental pathogen

8

Lancefield classification

An antigenic carbohydrate found in cell walls that determines the Lancefield groups

9

Capsular polysaccharide is used to classify what?

Antigenic specificity of S. Pneumoniae

10

Strep pneumo disease

- pneumonia (lobar type)
- bacteremia (invasion of tissues and multiplication in the blood)
- Otitis media- infectionsof the ear
- Meningitis: systemic infection which crosses the bbb
case fatality rate of 30 %

11

Strep pneumo can alter vascular permeability to allow access to blood stream leading to bacteriemia. Can then directly invade endothelial cells. Cross the blood brain barrier by binding to cerebral capillaries, then transmigrate and enter CSF leading to meningitis

ok...KNOW

12

Strep pneumo virulence factors

- Capsule- interferes with phagocytosis by leukocytes. Interferes with binding of complement to cell surface

- Pilli: The initial event in invasive pneococcus disease is the attachment of encapsulated pneumococci to epithelial cells in the URT.

- Cell wall components-

- Choline binding proteins: major pneumococcal adhesin. Intereacts with carbohydrates on the pulmonary epithelial surface. Important in crossing the blood brain barrier during development of meningitis

- Hemolysins: cause lysis of host cells and activate complement

- Hydrogen peroxide

- Neuraminidase and IgA proteas: Importan tin invasion and destruction of secreted IgA at the mucosal surface.

13

Two vaccines for strep pneumo

1) Pneumovax: MULTIVALENT, NON-CONJUGATED, 23 capsule types, for older patients and high risk groups like: HIV, cardiopulmonary, transplant patients, splenic disorders.
Lasts 5-7 years
not effective in infants and young
Protects against invasive pneumococcal disease

2) Prevnar: Heptavalent, 13 groups, conjugated
safe but expensive. Good for infants

14

Neisseria morphology

gram negative, non-motile that occur in pairs (diplococci)

15

Many Neisseria are part of normal flora

- Two pathogenic neisseria:
Neisseria Gonorrhoea- high prevalence, low mortality
Neisseria Meningitidis: cause of meningococcal meningitis and sepsis. Low prevalence but high mortality

16

So if someone is talking about meningococcus meningitis they are referring to what bacteria

Neisseria meningitidis

17

N. Meningitidis has a prominent antiphagocytic polysaccharide capsule. This differentiates it from N Gonorrhaea

KNOW

18

What Neisseria meningitidis subgroups cause sporadic (small) outbreaks

B,C,Y

N.M is grouped on the basis of their capsular polysaccharide into 12 serogroups. Those associated with disease are
A, B, C, Y W125

19

Epidemic neisseria meningitidis?

Serotype A

20

Meningitis belt

sub-saharan africa

- epidemics occur every 5-12 years, last for 2-3 dry seasons and die out during intervening rainy season

21

Pathogeneisis of fulminant meningitis from neisseria

Begins abruptly with sudden high fever, stiff neck, chills, myalgias, weakness, NAUSEA, VOMITTING, and headache. Aprehension, restlessness, delirium. Widespread petechial and skin lesions appear suddenly.

Pulmonanry insufficiency then develops and patients will die

22

Major toxin of N Meningitidis=

lipooligosaccharide- endotoxin (elicit strong immune response)

the antiphagocytic capsule is also important

23

Only known reservoir of N meningitidis

human nasopharynx...spread via respiratory droplets. Aspiration of the infective particles

24

Meningococci attach to the nonciliated columnar epithelium of the nasopharynx. Attachment is mediated by pili and possibly other outer membrane components. Invasion of the mucosal cells occurs by a mechanism that involves phase variation (turning off capsule genes then turning them back on once they get in the bloodstream.

KNOW

25

DOC for meningococcemia

Penicillin

26

Menomune

N menigitidis vaccine against serogroups A, C, Y, W135
- Unconjugated so there is no memory cmponent
- given to high risk and military
- controls epidemics

27

Menactra

Vaccine for serogroups A, C, Y, W135
licensed for use in 11-55 yo
Conjugate so there is memory
Given to all children 11-12 yo

28

Neither vaccine covers what serogroup?

B

29

High frequency genetic variation of N meningitidis?

Phase variation: changes in expression of a gene leading to on-off control. Remember slip/strand misparing. Many systems employ phase variation

Antigenic Variation: Changes in genes leading to expression of different forms of similar genes. Often involves the pili

30

Review phase variation slide 26

ok