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Streptococcus Flashcards

1
Q

Family Streptococcaceae
• Divided into 3 genera: (Bergey’s Manual of Determinative Bacteriology

A

)
• Streptococcus
• Enterococcus
• Lactococcus

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2
Q

Streptococci: General Characteristics
• Gram Positive Cocci in pairs or chains
• CATALASE____
• Fastidious → media??
• Colonies:_____
• With____ hemolytic zones
• Facultative anaerobes & needs_____ for growth
• Non-motile & Non-spore forming

A

Negative

BAP, CAP, Todd-Hewitt broth

Small, pinpoint, and translucent

large

5-10% CO2

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3
Q

Streptococci: Classification

A

• Patterns of Hemolysis
• Physiologic Requirement
• Lancefield Antigen Grouping

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4
Q

: Antigenic character in the polysaccharide cell wall

A

• Lancefield Antigen Grouping

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5
Q

: Antigenic character in the polysaccharide cell wall

A

• Lancefield Antigen Grouping

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6
Q

(Smith & Brown Classification)
J.H. Brown, 1919

A

Patterns of Hemolysis

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7
Q

Alpha hemolytic
• Incomplete or partial hemolysis of RBC
• green discoloration

A

S. pneumoniae
S viridans

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8
Q

Beta hemolytic
• complete hemolysis of RBC
• clear or colorless zone of hemolysis surrounding bacterial colony

A

S pyogenes
S agalactiae

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9
Q

Gamma hemolytic
Non-hemolytic

A

Enterococcus

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10
Q

(Bergey’s/Academic Classification)
Sherman 1937

A

Physiological Division

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11
Q

→ includes beta hemolytic strains ABCEFG

A

Pyogenic division

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12
Q

> not beta hemolytic, not salt tolerant, and grow at high pH

A

Viridans division

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13
Q

> salt tolerant, grow at high pH, and Temp range of 10°C to 45°C

A

Enterococcus division

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14
Q

> not clinically significant & associated with dairy industry

A

Lactic division

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15
Q

• Divides the Streptococci into serologic groups
• A, B, C, D, E (first 5)

A

Rebecca Lancefield (1933)

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16
Q

Rebecca Lancefield (1933)

• Currently: almost____ groups = (A - H) & (K - T)
•____ Testing
• Clinically Significant:___

A

20

Serological

A, D, C, D, F, G

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17
Q

Beta Hemolytic Streptococcus

Lancefield group A

Lancefield group B

Lancefield group C & G

Lancefield group A, C, F & G

A

• S. pyogenes

• S. agalactiae

• S. dysgalactiae & S. equi

• S. anginosus

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18
Q

• Not a normal flora
• Most virulent for humans

A

Group A: Streptococcus pyogenes (GAS)

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19
Q

Disease:
• Bacterial pharyngitis
• Skin infections
• Invasive diseases

A

Group A: Streptococcus pyogenes (GAS)

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20
Q

• Complications:
• Rheumatic Heart Disease
• Acute Glomerulonephritis

A

Group A: Streptococcus pyogenes (GAS)

21
Q

Group A: Streptococcus pyogenes (GAS)

• Transmission:

A

• Person to person contact
• Aerosol droplets

22
Q

Group A: Streptococcus pyogenes (GAS)

Major Virulence Factors
CELL SURFACE ANTIGENS

A
  1. Hyaluronic acid Capsule
  2. M protein
  3. Group-specific cell wall antigen
  4. IgG & IgA-binding proteins
  5. C5a protease
  6. F protein
  7. Lipoteichoic acid
23
Q

• 80 types
• inhibits activation of complement
• Anti-phagocytic

24
Q

Group-specific cell wall antigen:
• Grp.A sugar:

A

Rhamnose-N-acetylglucosamine

25
• Binds to Fc region of IgG or lgA.
IgG & IgA-binding proteins
26
• cleaves C5a component of complement • inhibits neutrophil chemotaxis in vitro
C5a protease
27
* allows binding to fibronectin in pharyngeal epithelium
F protein
28
• attached to M protein. • may allow binding to fibronectin
Lipoteichoic acid
29
Group A: Streptococcus pyogenes (GAS) Major Virulence Factors ENZYMES & TOXINS
1. Streptokinase 2. Streptodornase 3. Hyaluronidase 4. Diphosphopyridine Nucleotidase 5. Pyrogenic Exotoxins / Erythrogenic Toxins A, B, C 6. Streptolysin O 7. Streptolysin S
30
: Fibrinolysin that lyses blood clots
Streptokinase
31
: degrades host DNA & RNA
Streptodornase
32
• Associated with the organism's ability to destroy WBCs
Diphosphopyridine Nucleotidase
33
• Associated with fever and rashes in scarlet fever • Streptococcal TSS
Pyrogenic Exotoxins / Erythrogenic Toxins A, B, C
34
• Antigenic (Anti-Streptolysin O) • Also produced by Group C & G • Oxygen labile
Streptolysin O
35
• Oxygen stable • surface hemolysin • Antiphagocytic • Toxic to various human cell types
Streptolysin S
36
Pathogenesis and Clinical Manifestations PYOGENIC DISEASES
• Erysipelas • Cellulitis • Impetigo • Streptococcal Pharyngitis
37
GAS pyogenes TOXIGENIC DISEASES
• Necrotizing fasciitis •Scarlet Fever •Streptococcal Toxic Shock Syndrome
38
GAS pyogenes
S. pyogenes grows in infected wound >>> Bacteria enter bloodstream & secrete exotoxin A >>> Fever, rash, shock, bacteremia, respiratory failure (50% death rate)
39
Post-streptococcal Diseases • Preceeded by skin or respiratory infections • Represents a hypersensitivity response • Immune-mediated
Rheumatic heart disease Acute rheumatic fever Acute glomerulonephritis
40
Diagnostic Laboratory Tests A. MICROSCOPIC: B. CULTURE:
• gram (+) cocci in pairs or chains • 18-24 hrs. • @ 37C with 5-10% CO2
41
GAS CULTURE: • BAP: white to gray pinpoint colonies, translucent, opalescent.
18-24 hrs. @ 37C with 5-10% CO2
42
GAS BAP: white to gray pinpoint colonies, translucent, opalescent.
• Wide zone of B-hemolysis • Contaminated (throat): BAP with SXT • Mucoid colonies: M-CHON (+)
43
GAS Diagnostic Laboratory Tests C. BIOCHEMICAL :
1. Catalase 2. BAP WITH SXT = 3. Taxo A/Bacitracin Disk test 0.02 to 0.04 unit Any zone of inhibition 4. PYR Test:
44
PYR Test: Pyrrolidonyl arylamidase test • Reagent:
L-pyrrolidonyl-2-naphthylamide
45
PYR test P-naphthylamide + p-dimethylaminocinnamaldehyde (PYRase) →
Pink color
46
GAS SEROLOGICAL TEST:
• ASO (anti-streptolysin 0) • Sero typing of specific M CHON
47
SCARLET FEVER SUSCEPTIBILITY TESTS
1. DICK TEST 2. SCHULTZ-CHARLTON TEST
48
• 0.1ml toxin (test arm) & 0.1ml toxoid (control arm) • Observe for 24 hrs. • (+) redness in test arm (1 cm) • Susceptible to scarlet fever
DICK TEST
49
: (blanching phenomenon) • Inject 0.1 mL of anti-toxin subcutaneously • (+) fadind o redness after 6 to 8 hours • Neutralization of erythrogenic toxin
SCHULTZ-CHARLTON TEST

Bacte LEC (51 decks)

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