Streptococcus

Question 1

Streptococcus

Answer 1

G+

Question 2

Streptococcus

pyogenes

Answer 2

􀀃pus􀀄-forming

Question 3

Some streptococci are typically seen

as

Answer 3

diplo-cocci:

Streptococcus pneumoniae

Question 4

pneumolysin

Answer 4

pneumolysin degrades
hemoglobin 􀀅 green
Green color sheen has
given the name
􀀃viridens􀀄 to many α-
hemolytic Streptococci
like the caries-causing:
S.mutans, S.mitis,
S.salivarius, S.sanguis

Question 5

Hemolysis

Answer 5

Beta hemolytic: S. Pyogenes and S. galactia

Question 6

Virulence factors.

Answer 6

M protein

Question 7

M protein

Answer 7

cell wall component, >100 serotypes, membraneanchored:
is an important virulence factor
cell wall semi-dry (fuzz)
M-protein +
lipoteichoic acid
Group A
streptococci Hfibrinogen
• anti-M antibodies prevent infection of S.pyogenes but many serotypes.
So protective immunity is type-specific
• M protein binds keratinocytes, the main cell type in outer skin layer
• M protein binds fibrinogen, blocking surface from complement system
components
• M protein binds complement control proteins
• Inhibits formation of opsonins by complement cascade

Question 8

M protein binds

Answer 8

keratinocytes, the main cell type in outer skin layer.
fibrinogen, blocking surface from complement system
components
- complement control proteins
• Inhibits formation of opsonins by complement cascade

Question 9

prevent phagocytosis: virulence factors (2)

Answer 9

Øcapsule: antibodies are ineffective against glycocalyx-covered surface antigens

Question 10

Virulence factors (3)
M protein anti-complement action through

Answer 10

Factor H

Capsular C3 peptidase destroys opsonizing C3b complement opsonization

Question 11

G protein (cell surface) binds

Answer 11

Fc of IgG, preventing phagocytosis based on FcReceptors

Question 12

C5a peptidase in Group

Answer 12

C5a peptidase in Group A Streptococci

Question 13

C3b Peptidase

Answer 13

Cleaves c3b. Fs’up opsonization

Question 14

Virulence factors (4): Membrane damaging toxins

Answer 14

Cytotoxins

Question 15

V4: Streptolysins

Answer 15

S,O. : Hemolysis (beta) and Lyse phagocyte membrans

Question 16

Superantigens

Answer 16

Overrides t cell specificity.

S. Pyrogens

Question 17

Scarlet Fever Virulence Factor

Answer 17

superantigen: SPE

Question 18

Pyroderma

Answer 18

pyrogenic SPE􀀁s
pyo = pus
derma = skin
skin infections of face, arms, legs

Question 19

Erysipelas

Answer 19

pyrogenic SPE􀀁s
erythros = red
pella = skin
bullae = blisters

Question 20

􀀂Flesh-Eating􀀃
Strept.pyogenes

􀀂streptococcal gangrene

Answer 20

Necrotizing.
Progression to deep, systemic
infection leads to multi-organ
failure and death.

Question 21

Acute Pharyngitis

Answer 21

Acute Pharyngitis = 􀀂Strep throat􀀃

Question 22

Glomerulonephrites

Answer 22

Type III hypersenstive

Question 23

rheumatic fever

Answer 23

Type II Hyper

Question 24

Acute Rheumatic Fever

Answer 24

Myocarditis, arthritis

Question 25

Heart Disease by Streptococci

Answer 25

Acute Rheumatic Fever:
• non-suppurative sequela with some strains
• <10% of population is susceptible
• fever is non-responsive to penicillin
because disease is autoimmune
• high frequency of reoccurrence

Question 26

Rheumatic Heart Disease by Streptococci

Answer 26

Leaking Mitral Valve

Question 27

Streptococcus agalactiae

Group B

Answer 27

β-hemolytic (<2% non-hemolytic), chain-like growth, aerobic, polysaccharide capsule
Normal occurrence in the lower gastrointestinal tract
Does not cause disease in healthy people
• pneumonia in neonates (neonates: <7 days of birth)
• bacteremia and meningitis (neonates: >7 days of birth)

Question 28

Streptococcus agalactiae

Answer 28

urinary infections, bacteremia (pregnant women)
Strains different from S.pyogenes or S.agalactiae may cause opportunistic
streptococcal toxic shock syndrome (see Ch.64)
e.g. in HIV-immune-compromised cases.
Neutralizing antibodies against group B polysaccharide Ag develop quickly and protect.
(maternal Ab􀀁s prevent infection of neonate)