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Flashcards in Virulence Factors Deck (14)
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1

Streptococcus Pneumoniae

Polysaccharide capsule
Pneumolysin
Hyaluronidase
Neuraminidase
Pili
Lipoproteins
Peptidoglycan adn teichoic acids
Choline-binding proteins
competence protein
Autolysin

2

Polysaccharide capsule

most important virulence factor for S. pneumoniae

antiphagocytic (except when anti-capsule antibodies...opsonic)

> 80 capsular types, can be identified by Quellung rxn.

most pneumonias are caused by 23 of the 80 types

3

Pneumolysin

pore-forming toxins (hemolysins)

binds cholesterol in host cell membranes-->pore-->cell lysis

Infection of lungs: recruits neutrophils and lymphocytes= more inflammation; interacts w/ TLR4-->stimulates cytokine production

Infection of meninges: especially bad if bacteriolytic antibiotics are used

breaks down hemoglobin into green pigment-->alpha hemolysis

4

Hyaluronidase

aids spread of bacteria in hyaluronic acid tissues

5

Neuraminidase

clips N-acetylneuraminic acid from cell surface glycoproteins

may 1) cause direct damage, or
2) unmask binding sites for pneumococci

loss of neuraminic acid=spread of pneumococci along Eustachian tube towards middle ear

6

Pili

LPXTG-sortase mechanism-->polymer of pilus protein monomers

adhesion to epithelial cells

7

Lipoproteins

cell surface molecules important in various ways

i.e. iron uptake

8

Peptidoglycan and teichoic acids

main cell wall components

Wall teichoic acid
lipoteichoic acid
C-Polysaccharide

Also stimulate inflammation b/c recognized by pathogen recognition receptors (i.e. TLRs)--> cytokine secretion

9

Wall teichoic acid (WTA)

long polyglycerolphosphate moity covalently bound to peptidoglcan petide crossbridges

very negatively charged molecule

10

Lipoteichoic acid (LTA)

polyglycerolphosphate moity bound in different way
diacylglycerol moity on one end and two fatty acids intercalated into membrane

negativity of LTA and WTA neutrolyzed by linking choline instead of D-alanine

11

C--polysaccharide

teichoic acid and adherent fragments of peptidoglycan

bound by CRP-->complement activated--> inflammation

12

choline-binding proteins (CBPs)

up to 10

anchored tto cell surface via repeat domains that bind to choline in cell wall

1) several are hydrolytic enzymes involved in virulence through release of cell wall fragments that stimulate inflammation (i.e. LytA)

2) Others bind to nasopharyngeal or lung epithelium (i.e. PsaA)

3) PspA and PspC inhibit phagocytosis by binding complement factor H

4) Binding to polymeric immunoglobulin receptor aids in transepithelial transport necessary for deep tissue invasion

5) Adhesion to platelet-activating factor receptor important in invasion of CNS

13

Competence protein

enables pneumococci to acquire DNA from environment

14

Autolysin, LytA

disrupt cell wall formation

important in cell wall remodeling during cell division

can also cause bacteria to lyse--> release of cell wall fragments--> activation of immune system