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Flashcards in Virulence factors Deck (48):
1

endotoxin

component G- bacterial cell wall
released when bacterial cell die
LPS (or LOS)

2

Lipid A

Portion of LPS.

highly conserved endotoxin forming outer leaflet of outer membrane.

TOXIC!

if cell can't make lipid A, can't survive

3

O-Antigen

antigenic portion of LPS. Non-toxic.

adhesion to host lectins

4

G- immune response

Lysis of G- bacteria --> LPS --> Lipid A binds to CD14 and TLR4 on macrophage --> cytokines (IL-1, IL-6, IL-8, TNFalpha, PAF)

5

G+ immune response

Lysis of G+ bacteria --> Peptidoglycan fragments & Lipotechoic acid --> binds to TLR2 and TLR6 on macrophage --> activates transcription --> cytokines (IL-1, IL-6, IL-8, TNFalpha, PAF)

6

pyrogen free

free of LPS endotoxin (lipid A)

7

How do you vizualize a bacterial capsule?

Quellung Reaction

or

Fluorescent antibodies

8

What is the Quellung reaction?

antibodies bind to the bacterial capsule

The antibody rxn allows these species to be seen under microscope.

If reaction is positive, the capsule becomes opaque and appears to enlarge.

ex:
Streptococcus pneumoniae, Klebsiella pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Escherichia coli, and Salmonella.

9

how do capsules block phagocyte receptor binding? (3 ways)

1)negative charge (acidic) capsules repel phagocyte
2) cover components of baterial cell surface recognizable to phagocyte receptor
3) reduce complement activity --> sialic acid

10

what is sialic acid?

component of some bacterial capsules. It binds factor H & chews up complement so complement can't destroy bacteria.

It is NOT antigenic

11

exotoxin

protein secreted by bacterial cell --> disease symptoms

12

superantigen

binds MHCII & TCR w/o antigen present (non-specific T cell activation). It is a type of exotoxin.

13

What are three examples of superantigen exotoxins?

1) staphylococcal enterotoxins
2) TSS toxin
3) streptococcal pyrogenic toxins

14

what is quorum sensing?

in biofilms, bacteria secrete "autoinducer" which activates transcriptional regulators when reaches sufficient concentration.

ex: G- bacteria grow together.
@low density --> QS can't bind
@high --> QS signal-receptor complex forms

15

staph aureus's exotoxin virulence factor?

alpha-toxin (exotoxin)

pore-forming toxin. Alpha-toxin inserts into membrane, oligomerizes and forms pores which leads to cell lysis

16

What bacteria and exotoxin lead to gas gangrene?

Claustridium perfringens

alpha toxin = PLC enzyme
it degrades cell membrane which leads to lysis of cell. This leads to decrease in muscle blood flow which leads to occlusive plugs and results in low oxygen environment which is favorable for bacteria.

17

Diptheria Toxin

Intracellular exotoxin

B binds cell membrane, A breaks off and inactivates (ADP-ribosylates) elF2 which is necessary for protein synthesis inside of cells.

18

What bacterium has same MOA as diptheria exotoxin?

Corynebacterium Diptheria

19

Vibrio cholerae toxin

toxin permanently activates Gs which INCREASES cAMP --> CFTR channel continually activated --> Diarrhea

20

Effectors

type of intracellular exotoxin

encoded in pathogenicity islands

injected into host cell by type III "Injectisome"

21

Botulinum

"floppy baby", flaccid paralysis

22

Tetanus

rigid paralysis

23

what medium do Neisseria meningitides grow?

Chocolate agar or thayer martin

24

what is the main virulence factor for neisseria meningitides & Pathogenesis?

Invasion and growth in blood stream via capsule --> LOS released while organism is intact --> Lipid A released which blebs --> inflammatory response --> increases permeability of capillaries --> shock & DIC

25

which serogroups on capsule in neisseria meningitidis most commonly cause serious disease?

B, C, Y (causes most), W-135, A

26

what are the clinical features of meningitis?

-common in college aged students
- neck stiffness, rash
- fever, nausea, vomiting, myalgia
- petechial rash!

27

What color does Pseudomonas aeruginosa stain?

blue-green pigment with fruity odor (pus can be colored and useful for diagnosis)

28

what is the main virulence factor of pseudomonas aeruginosa and what is the pathogenesis?

Exotoxin A

ADP ribosylates elF2 on diphthamide residue

A functions same as diptheria
B has different specificity

29

what are the cytolysins of P. aeruginosa?

1) Phospholipase C
2)Rhamnolipid
3) leukocidin

30

What type III exotoxins exist with P. aeruginosa?

1) ExoS (alters cell shape and prevents DNA synthesis) & ExoT (inhibits phagocytosis)
2)ExoU- Phospholipase that causes cell necrosis and is associated with more virulent, fulminant disease

31

what are exoenzymes and what bacteria are they important for?

"spreading factors" responsible for signficant tissue damage and faciliate spread through tissue by degrading immune components and reducing effeective response

ex: elastases-- lung damage)

32

CFTR mutation exacerbated by which bacteria?

P. aeruginosa

chronically infects by age 20. causes chronic inflammation and bouts of pneumonia. Causes most inflammation and is major cause of morbidity and mortality

33

pathogenesis in CF lung (P. aeruginosa)

forms biofilm with other species and this leads to persistent infection, chronic inflammation and impedes gas change.

exacerbation with fever and increases sputum production

eventually lungs fail

34

Alginate

polysaccharide virulence factor associated with p. aeruginosa.

it is a component of mature biofilm that initially isolates from CF infections that are non-mucoid. It switches to mucoidy. It is linked to severe disease

35

what exopolysaccaride virulence factors are associated with P. aeruginosa?

Pel and Psl polysaccharides

regulated by quorum sensing

36

what reservoir does staph aureus colonize?

nose

37

hand hygene is shown to cut down infection rates in hospitals of what bacteria?

s. aureus

38

which types of capsule are linked to severe illness in S. Aureus?

5 and 8

39

Protein A is major virulence factor for what bacteria and how does it work?

S Aureus.

Binds Fc portion of IgGs. Prevents complement from binding same region, prevents phagocytosis

40

which cytolysins are important virulence factors for staph aureus?

alpha-toxin = forms pore in membrane, targets PMNs in infection

beta-toxin = sphingomyelinase

gamma-toxin = Planton-Valentine Leukocidin (PVL), pore forming that is carried most often by strains causing community-causing infection and more severe symptoms (takes out WBCs)

41

Staphyloccal food poisoning is caused by what?

ingestion of preformed staph enterotoxins (SEA, SEB, SEC)

42

Toxic Shock syndrome is caused by what? and is associated with which bacteria?

superantigens

s. aureus

43

Menstrual TSS

hyperabsorbant tampon use
S. aureus already present in vagina.
bacteria induced to produce: TSST-1!!! = pyrogenic exotoxin C, enterotoxin F

bacteria not found in bloodstrea-- toxin migrates through mucosa

44

Non-menstrual TSS

colonization of infection somewher ein body (i.e. nose-- usually deep tissue, bacteremia)

half of cases due ot strains producing TSST-1 and other half produce SEB/SEC

45

Staph. Scalded skin syndrome

most seen in infants

EXFOLIANTS produced by colonizing and infecting bacteria.

Bind GM4 ganglioside and degrade desmosomes (top layer of skin separates)

46

bulbous impetigo

localized form of scalded skin syndrome. Toxin (exfoliantins) limited to site of production by anti-exfoliatin Abs, bacteria present in blisters can be cultured. Vs. Generalized form where you cannot culture causative agent.

47

What is Listeria's virulence factor? and what is its mechanism of action?

Listeriolysin O, a phospholipase, punches hole in phagosome allows pathogen to escape from phagolysosome.

48

What are 2 membrane damaging exotoxin mechanisms and one surfactant?

1) pore-forming toxins (i.e. staph aureus alpha toxin)

2)enzymatic lysis (alpha toxin-PLC, claustridium perfringens)

3) pathogen escape from phagolysosme (listeriolysin O, Listeria)