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B2.2 GROUP A STREPTOCOCCI Flashcards

1
Q

GROUP A STREPTOCOCCI SPP

A

Streptococcus pyogenes

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2
Q

How is Group A Streptococcus acquired?

A

Through contaminated droplets from coughing and sneezing

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3
Q

Where does Streptococcus pyogenes colonize in humans?

A

Throat and skin

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4
Q

S. pyogenes is resistant to drying that is why this method is used for acquiring specimen

A

can be recovered from swabs several hours after the collection

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5
Q

VIRULENCE FACTORS of S. pyogenes

A

1.M PROTEIN
2. PROTEIN F
3. LIPOTEICHOIC ACID
4. HYALURONIC ACID CAPSULE
5. STREPTOKINASE
6. HEMOLYSINS
7. DEOXYRIBONUCLEASE (DNASE)
8. HYALURONIDASE
9. C5a PEPTIDASE
10. Streptococcal Pyrogenic Exotoxins (SPEs)

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6
Q

What major virulence factor of Streptococcus pyogenes resists phagocytosis and adherence of the bacterial cell to mucosal cells

A

M protein

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7
Q

M protein is found in what part of S. pyogens

A

attached to peptidoglycan of cell wall and extends to cell surface

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8
Q

What are the post-streptococcal diseases and what M protein mediates them

A

Rheumatic fever - class 1 M
Acute glomerulonephritis - class I or II

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9
Q

regulatory protein involved in the degradation of C3b

A

beta globulin factor H

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10
Q

M protein binds to what proteins in S. pyogenes

A

beta globulin factor H
fibrinogen

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11
Q

What serotype of M protein is most common in pharyngitis?

A

M1 serotype

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12
Q

Which post-streptococcal diseases are mediated by M protein?

A

Rheumatic fever (Class I M) and Acute glomerulonephritis (Class I or II)

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13
Q

What is the function of Protein F in Streptococcus pyogenes?

A

Mediates epithelial cell attachment

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14
Q

PROTEIN F is also known as

A

FIBRONECTIN-BINDING PROTEIN

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15
Q

What molecule in Streptococcus pyogenes is responsible for adherence to respiratory epithelial cells?

A

Lipoteichoic acid

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16
Q

Prevents opsonized phagocytosis and masks bacterial antigens

weakly immunogenic

A

hyaluronic acid capsule in Streptococcus pyogenes

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17
Q

Lysis of fibrin clots to spread infection

binds plasminogen and activates the production of plasmin

allows bacteria to move from clotted area (spread infecion)

A

streptokinase

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18
Q

What is the clinical application of streptokinase?

A

Treatment of pulmonary emboli, coronary artery, and venous thromboses

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19
Q

HEMOLYSINS types

A

STREPTOLYSIN O (SLO)
STREPTOLYSIN S (SLS)

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20
Q

Which hemolysin of Streptococcus pyogenes is oxygen labile?

A

Streptolysin O (SLO)

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21
Q

Which hemolysin of Streptococcus pyogenes is oxygen stable?

A

Streptolysin S (SLS)

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22
Q

Hemolysin

responsible for subsurface hemolysis on BAP incubated anaerobically
causes lysis of RBC, WBC, platelets, tissue cells

A

STREPTOLYSIN O (SLO)

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23
Q

STREPTOLYSIN O (SLO) is inhibited by

A

cholesterol in skin lipids

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24
Q

What test detects antibodies against Streptolysin O?

A

Anti-Streptolysin O (ASO) test

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25
Q

surface hemolysis seen around colonies that have been incubated aerobically

causes lysis of RBC, WBC and platelets in the presence of room air

nonimmunogenic

A

STREPTOLYSIN S (SLS)

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26
Q

STREPTOLYSIN S (SLS) inhibited by

A

nonspecific inhibitor that is frequently present in sera of humans and animals

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27
Q

What is another name for streptococcal deoxyribonuclease (DNase)

A

Streptodornase

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28
Q

lowers viscosity of exudates, giving pathogens more mobility

A

DEOXYRIBONUCLEASE (DNASE)

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29
Q

How many types of DNase are there, and which is most common?

A

Four types; DNase B is the most common

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30
Q

solubilizes the ground substance of mammalian connective tissues
antigenic and specific for each bacterial or tissue source

A

hyaluronidase

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31
Q

HYALURONIDASE
aka

A

SPREADING FACTOR

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32
Q

serine protease capable of inactivating the chemotactic factor for neutrophils and monocytes (C5a)

A

C5a PEPTIDASE

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33
Q

What does C5a peptidase inactivate?

A

The chemotactic factor C5a

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34
Q

What are streptococcal pyrogenic exotoxins (SPEs) formerly called?

A

Erythrogenic toxins

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35
Q

Cause scarlet fever rash and act as superantigens inducing immune mediator release

A

streptococcal pyrogenic exotoxins

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36
Q

Streptococcal Pyrogenic Exotoxins (SPEs) heat reaction and rarely found in what groups

A

heat labile and rarely found in group C and G

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37
Q

act as SUPERANTIGENS activating macrophages and T helper cells

A

Streptococcal Pyrogenic Exotoxins (SPEs)

38
Q

SPEs induce release of powerful immune mediators such as

and causes what

A

IL-1,
IL-2,
IL-6,
TNF-alpha,
TNF-beta,
interferons, and
cytokines

shock and organ failure

39
Q

What are the four types of streptococcal pyrogenic exotoxins?

A

SpeA, SpeB, SpeC, and SpeF

40
Q

What disease is associated with streptococcal pyrogenic exotoxins?

A

Streptococcal toxic shock syndrome

41
Q

What exotoxin degrades proteins and mediates the rash in scarlet fever?

A

Exotoxin B (cysteine protease)

42
Q

RELATED INFECTIONS AND DISEASES with S. pyogenes

A
  1. BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT)
  2. PYODERMAL INFECTIONS
  3. NECROTIZING FASCIITIS
  4. STREPTOCOCCAL TOXIC SHOCK SYNDROME
  5. SCARLET FEVER (SCARLATINA)
  6. POSTSTREPTOCOCCAL SEQUELAE
43
Q

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT)
 Incubation period
MOT
Diagnosis

A

1 to 4 days
spread by droplets and close contact
culture of specimen (throat swabs) or direct antigen detection

44
Q

highly virulent strains can cause sharp outbreaks of sore throats and scarlet fever in schools and camps

A

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT)

45
Q

BACTERIAL PHARYNGITIS OR TONSILLITIS (STREP THROAT) additional risks when infecting infants and small children

A

tendency to extend to the middle ear and mastoid

46
Q

PYODERMAL INFECTIONS

A

Impetigo
Erysipelas
Cellulitis

47
Q

localized skin disease that begins as small vesicles that progress to weeping lesions that crust over after several days

usually seen in young children (2 to 5 years)

48
Q

acute spreading skin lesion that is intensely erythematous with a plainly demarcated but irregular edge

rare infection of the skin and subcutaneous tissues observed frequently in elderly patients

A

Erysipelas

49
Q

diffuse, spreading infection of subcutaneous skin tissue characterized by defined area of redness (erythema) and the accumulation of fluid (edema)

follows infection associated with mild trauma, burns, wounds, or surgical incisions

may lead to gangrene

A

Cellulitis

50
Q

Cellulitis is Differentiated from erysipelas by two clinical findings

A

lesion is not raised
line between the involved and uninvolved tissue is indistinct

51
Q

NECROTIZING FASCIITIS is also known as

A

GALLOPING GANGRENE,
FLESH-EATING BACTERIA SYNDROME, SUPPURATIVE FASCIITIS,
HOSPITAL GANGRENE, or
NECROTIZING ERYSIPELAS

52
Q

invasive infection characterized by rapidly progressing inflammation and necrosis of the skin, subcutaneous fat, and fascia

A

NECROTIZING FASCIITIS

53
Q

Component of S. pyogenes that acts as a superantigen, causing the immune system to contribute to the damage of Necrotizing fasciitis

A

Exotoxin A

54
Q

NECROTIZING FASCIITIS type

polymicrobial infection from which aerobic and anaerobic bacteria are recovered

55
Q

NECROTIZING FASCIITIS type

GAS

56
Q

NECROTIZING FASCIITIS type

gas gangrene or clostridial myonecrosis

57
Q

characterized by a precipitous drop in blood pressure, failure of multiple organs, and a very high fever

caused by an invasive strep A that produces one or more of the streptococcal pyrogenic exotoxins

initial streptococcal infection includes pharyngitis, peritonitis, cellulitis, wound infections

A

STREPTOCOCCAL TOXIC SHOCK SYNDROME

58
Q

play a major role in the pathogenesis of the disease (STSS) = superantigens

59
Q

most common strains associated with
streptococcal TSS

60
Q

punctate exanthem overlying a diffuse erythema that appears initially on neck and upper chest, 1 to 2 days following strep throat

rash disappears over the next 5 to 7 days and is followed by desquamation

communicable and spread by inhalation of infectious respiratory droplets

results from a throat infection with a strain of S. pyogenes that carries lysgenic bacteriophage (T12)- cause by release of streptococcal pyrogenic exotoxins

A

SCARLET FEVER (SCARLATINA)

61
Q

SCARLET FEVER (SCARLATINA) cardinal signs

A

diffuse red rash on the upper chest and spreads to the trunk and extremities, and “strawberry-colored” tongue

62
Q

TEST FOR SCARLET FEVER

A

a. DICK’S TEST
b. SCHULTZ- CHARLTON TEST

63
Q

susceptibility test for scarlet fever

A

DICK’S TEST

64
Q

DICK’S TEST

 Test arm:
 Control arm: :
 Read reaction after

A

 Test arm: 0.1 ml of Dick’s toxin (Eryhtrogenic Toxin)

 Control arm: : 0.1 ml of Dick’s toxoid

 Read reaction after 24 hours

65
Q

DICK’S TEST 
(+) reaction
Interpretation

A

Eythema or redness in the test site

Susceptible to scarlet fever

66
Q

based on neutralization of eryhtrogenic toxins when anti-toxin is injected on the skin of patient with scarlet fever

diagnose whether rashes of patient is due to scarlet fever or not

A

SCHULTZ- CHARLTON TEST

67
Q

SCHULTZ- CHARLTON TEST (+) reaction:

A

“BLANCHING PHENOMENON” – fading of the
rashes

68
Q

POSTSTREPTOCOCCAL SEQUELAE diseases

A

RHEUMATIC FEVER
ACUTE GLOMERULONEPHRITIS

69
Q

follows S. pyogenes pharyngitis

autoimmune disease characterized by fever and inflammation of the heart, joints, blood vessels, and subcutaneous tissues

mediated by antibodies produced against S. pyogenes M protein that cross-react with human heart tissue

A

RHEUMATIC FEVER

70
Q

Rheumatic fever most serious result

A

chronic, progressive damage to the heart
valves

71
Q

most common cause of permanent heart valve damage in children

A

RHEUMATIC FEVER

72
Q

ACUTE GLOMERULONEPHRITIS is also known as

A

BRIGHT’S DISEASE

73
Q

 inflammatory disease of the renal glomeruli

 develops 1–4 weeks after S pyogenes skin infection (pyoderma, impetigo) or respiratory infection

deposition of antigen-antibody complexes, possibly involving the streptococcal M protein

 Type III hypersensitivity reaction

A

ACUTE GLOMERULONEPHRITIS

74
Q

Specimen of choice for diagnosing S. pyogenes

A

Pharynx and Tonsillar Swabs (Throat Swabs)

75
Q

Laboratory diagnosis methods for S. pyogenes

A
  1. Culture Medium
  2. Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U)
  3. Pyrrolidonyl-α-Naphthylamide Hydrolysis Test
  4. Sulfamethoxazole and Trimethoprim Test
  5. Serologic Test: ASO TEST
  6. Anti-DNase B Testing
76
Q

Culture Medium choice and appearance of S. pyogenes in media

A

BAP: colonies are transparent to translucent, convex or domed entire, circular, shiny and surrounded by wide zone of βhemolysis

77
Q

presumptive identification of S. pyogenes (S)
screening for GAS in throat cultures
groups C and G are also susceptible

A

Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U)

78
Q

Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U) result for S. pyogenes

A

Susceptibility or any zone of inhibition

79
Q

Which species is resistant to Bacitracin Susceptibility Test/Taxo A (0.02-0.04 U)

A

S. agalactiae

80
Q

detects L-pyrrolidonyl arylamidase
more specific for S. pyogenes than bacitracin
 S. pyogenes is the only species of Streptococcus that is positive with PYR test

A

Pyrrolidonyl-α-Naphthylamide Hydrolysis Test

81
Q

Pyrrolidonyl-α-Naphthylamide Hydrolysis Test detects what

A

L-pyrrolidonyl arylamidase

82
Q

Other PYR(+) species

A

Enterococcus, Aerococcus, and Gemella

83
Q

Positive result for S. pyogenes when using Pyrrolidonyl-α-Naphthylamide Hydrolysis Test

A

Cherry Red color

84
Q

Sulfamethoxazole and Trimethoprim Test resistant groups (positive result)

A

Group A and B streptococci

85
Q

Sulfamethoxazole and Trimethoprim Test susceptible groups (negative result)

86
Q

interfering respiratory microbiota will be inhibited by SXT

(+) result: Resistance

A

Sulfamethoxazole and Trimethoprim Test

87
Q

 Serum is added with measured amount of SLO reagent and incubated
 Reagent RBC are added  indicator
 Enough antibody is present: SLO neutralized and no hemolysis occurs

A

Serologic Test: ASO TEST

88
Q

reciprocal of the highest dilution demonstrating no hemolysis expressed in TODD units

89
Q

neutralize reagent DNase B, preventing it from depolymerizing DNA

A

Anti-DNase B Antibodies

90
Q

DNase measured by its effect on a DNA methyl-green conjugate

A

Anti-DNase B Testing

BACTERIOLOGY (32 decks)

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