Strep Pyogenes

Question 1

what are the group A streptococci?

Answer 1

strep pyogenes

Question 2

is streptococcus catalase + or -?

Answer 2

it is catalase negative

Question 3

will strep pyogenes be sensitive or resistant to bacitracin?

Answer 3

it will be sensitive

Question 4

what are the 3 virulence factors for strep pyogenes?

Answer 4

M protein *

Streptolyin O*, streptolysin S

Streptococcal pyrogenic exotoxins (SPEs)

Question 5

if cultivated on blood agar, it will cause what hemolysis?

Answer 5

beta-hemolytic

Question 6

what does the M protein in strep pyogenes do?

Answer 6

• Mediates adherence to host cell
• Facilitates invasion of host cell
• Anti-phagocytic
  
  • blocks binding of complement C3 to bacterial cell wall preventing phagocytosis
  • Binds Fc portion of opsonizing antibodies preventing phagocytosis

Question 7

what does Streptolysin O * do?

Answer 7

• Lyses RBCs, leukocytes, platelets
• It is Antigenic (stimulates antibody production)

Question 8

how can streptolysin O be detected?

Answer 8

using ASO

Question 9

what do streptokinases do?

Answer 9

• causes Lysis of clots and fibrin deposits *
• Facilitates spread of infection

Question 10

what does C5a peptidase * do?

Answer 10

Degrades C5a  reduced complement-mediated inflammation

Question 11

what do the Streptococcal pyrogenic exotoxins (SPEs)* do?

Answer 11

• Cause the rash of scarlet fever
• Produced by Streptococcal TSS strains
• can be Superantigen *
  
  • Interacts with both macrophages & T cells causing non-specific activation of T cells
  • This results in release of large amts of cytokines (IL-1, IL-2 TNF-α)

Question 12

what diseases does strep pyogenes cause?

Answer 12

phrayngitis (Strep Throat)

scarlet fever

skin and soft tissue infections

strep toxic shock syndrome

Question 13

what is the most common cause of bacterial pharyngitis?

Answer 13

strep pyogenes

Question 14

how is phrayngitis (strep throat) diagnosed?

how is the diagnosis confirmed?

Answer 14

rapid strep antigen test

confirmed on culture

Question 15

can strep throat be left untreated and self-resolves? WHY?

Answer 15

NO! must treat with antibiotics

if left untreated may lead to rheumatic fever

Question 16

what is this?

Answer 16

strep throat

Question 17

what is this?

Answer 17

strep throat

Question 18

what 2 complications can result from strep throat (strep pharyngits)?

Answer 18

Rheumatic fever and Scarlet Fever

Question 19

what will cause the scarlet fever complication?

Answer 19

Group A strep producing pyrogenic exotoxin from strep pyogenes

Question 20

how does scarlet fever present to in a clinic?

Answer 20

Erythematous rash *that starts in upper chest and spreads to extremeties

strawberry tongue

Question 21

what is this?

what is this a consequence of?

who causes this?

Answer 21

erythemathous rash

scarlet fever

strep pyogenes

Question 22

what is this?

Answer 22

strawberry tongue in scarlet fever

Question 23

what skin and soft tissue infections does strep pyogenes cause?

Answer 23

impetigo

cellulatis

erysipelas

necrotizing fasciitis

Question 24

what is this?

Answer 24

impetigo

Question 25

impetigo looks like what other infection?

Answer 25

staph aureus

Question 26

impetigo infection lesion is described as what?

Answer 26

honey-crusted lesions

Question 27

what is erysipelas?

Answer 27

acute inflammation of the **deep** dermis and **upper subcutis** by strep

Question 28

does erysipelas spread?

Answer 28

yes

Question 29

what is the presentation for erysipelas?

Answer 29

lesions that present as hot, painful, red, raised

Question 30

what will erysipelas lead to if left untreated?

Answer 30

respiratory tract or skin infection

Question 31

what is this?

Answer 31

erysipelas

Question 32

what is cellulitis? what differentiates cellulitis from erysipelas?

Answer 32

Deeper infection than erysipelas No clearly demarked separation between normal and infected skin

Question 33

what is necrotizing fasciitis?

Answer 33

Bacteria spreads along superficial and deep fascial planes and enters following minor trauma, or hematogenous spread from Group A Strep throat infection to site of blunt trauma/muscle strain

Question 34

what will necrotizing fasciitis cause?

Answer 34

extensive destruction of muscle and fat \*

Question 35

what is a major risk factor to developing necrotizing fasciitis?

Answer 35

History of recent varicella-zoster virus (VZV) infection

Question 36

what is this?

Answer 36

necrotizing fasciitis

Question 37

what strains of streptococci will cause strep toxic shock syndrome?

Answer 37

* prominent capsule and SPEs (pyrogenic exotoxin - superantigen) \* * M1 and M3 serotypes * Preceding skin infection (eg cellulitis)

Question 38

what will differentiate strep toxic shock syndrome from staph toxic shock syndrome?

Answer 38

Blood cultures positive for Strep pyogenes\*, the bacteria will in the blood (bacteremia)

Question 39

strep bacteremia usually follows what 2 diseases?

Answer 39

necrotizing fasciitis or toxic shock syndrome

Question 40

what are the Non-suppurative Post-streptococcal sequelae? (complication from giving antibiotics)

Answer 40

Rheumatic fever Acute glomerulonephritis

Question 41

how do you diagnose rheumatic fever in a untreated strep throat?

Answer 41

positive serologic tests (ASO)\* will be negative for the bacteria in the throat or blood

Question 42

why will rhumatic fever damage the heart, joints, skin andbrain?

Answer 42

Anti-streptococcal antibodies cross-react with tissues of the heart (mitral and aortic valves) \*

Question 43

what is rheumatic heart disease?

Answer 43

damage to the mitral and aortic valces (stenosis) 10-20 years after infection

Question 44

what is acute glomerulonephritis? what does it present with?

Answer 44

immune-complex disease present with: hematuria, proteinuria, smoky/coal-colored urine

Question 45

what has to happen to get glomerulonephritis strep pyogenes related?

Answer 45

Follows cutaneous infection, or pharyngitis \*

Question 46

how do you test for glomerulonephritis?

Answer 46

positive anti-DNAse B & ASO

Question 47

What antibody tests do you use to verify rheumatic fever?

Answer 47

positive ASO for ARF \*

Question 48

What test do you use to differentiate strep pyogenes from staph aureus?

Answer 48

PYR test positive for strep pyogenes

Question 49

how does strep pyogenes look under the microscope?

Answer 49

gram positive chains

Question 50

how do you treat group A diseases?

Answer 50

penicillin

Question 51

how do you treat pharyngitis by group A streptococcus?

Answer 51

oral penicillin/amoxicillin

Question 52

what if patient is allergic to penicillin, and they are afflicted with strep throat?

Answer 52

erythromycin

Question 53

how do you treat impetigo caused by strep A? what about impetigo caused by staph aureus?

Answer 53

nafcillin still use nafcillin

Question 54

strep throat penicillin will prevent development of what disease?

Answer 54

rheumatic fever

Question 55

what is DNases (streptodornases)? why are they important?

Answer 55

* Depolymerize free DNA * Antibodies to DNase B imp. marker for diagnosis of antecedent skin/throat infections \*