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Bacte LEC > Streptococcus > Flashcards

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

A

M protein

24
Q

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

A

Rhamnose-N-acetylglucosamine

25
Q

• Binds to Fc region of IgG or lgA.

A

IgG & IgA-binding proteins

26
Q

• cleaves C5a component of complement
• inhibits neutrophil chemotaxis in vitro

A

C5a protease

27
Q
  • allows binding to fibronectin in pharyngeal epithelium
A

F protein

28
Q

• attached to M protein.
• may allow binding to fibronectin

A

Lipoteichoic acid

29
Q

Group A: Streptococcus pyogenes (GAS)

Major Virulence Factors
ENZYMES & TOXINS

A
  1. Streptokinase
  2. Streptodornase
  3. Hyaluronidase
  4. Diphosphopyridine Nucleotidase
  5. Pyrogenic Exotoxins / Erythrogenic Toxins A, B, C
  6. Streptolysin O
  7. Streptolysin S
30
Q

: Fibrinolysin that lyses blood clots

A

Streptokinase

31
Q

: degrades host DNA & RNA

A

Streptodornase

32
Q

• Associated with the organism’s ability to destroy WBCs

A

Diphosphopyridine Nucleotidase

33
Q

• Associated with fever and rashes in scarlet fever
• Streptococcal TSS

A

Pyrogenic Exotoxins / Erythrogenic Toxins A, B, C

34
Q

• Antigenic (Anti-Streptolysin O)
• Also produced by Group C & G
• Oxygen labile

A

Streptolysin O

35
Q

• Oxygen stable
• surface hemolysin
• Antiphagocytic
• Toxic to various human cell types

A

Streptolysin S

36
Q

Pathogenesis and Clinical
Manifestations
PYOGENIC DISEASES

A

• Erysipelas
• Cellulitis
• Impetigo
• Streptococcal Pharyngitis

37
Q

GAS pyogenes

TOXIGENIC DISEASES

A

• Necrotizing fasciitis
•Scarlet Fever
•Streptococcal Toxic Shock Syndrome

38
Q

GAS pyogenes

A

S. pyogenes grows in infected wound
»> Bacteria enter bloodstream & secrete exotoxin A&raquo_space;>
Fever, rash, shock, bacteremia, respiratory failure (50% death rate)

39
Q

Post-streptococcal Diseases

• Preceeded by skin or respiratory infections
• Represents a hypersensitivity response
• Immune-mediated

A

Rheumatic heart disease
Acute rheumatic fever
Acute glomerulonephritis

40
Q

Diagnostic Laboratory Tests
A. MICROSCOPIC:

B. CULTURE:

A

• gram (+) cocci in pairs or chains

• 18-24 hrs.
• @ 37C with 5-10% CO2

41
Q

GAS

CULTURE:
•
BAP: white to gray pinpoint colonies, translucent, opalescent.

A

18-24 hrs. @ 37C with 5-10% CO2

42
Q

GAS

BAP: white to gray pinpoint colonies, translucent, opalescent.

A

• Wide zone of B-hemolysis
• Contaminated (throat): BAP with SXT
• Mucoid colonies: M-CHON (+)

43
Q

GAS

Diagnostic Laboratory Tests
C. BIOCHEMICAL :

A
  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
Q

PYR Test: Pyrrolidonyl arylamidase test
• Reagent:

A

L-pyrrolidonyl-2-naphthylamide

45
Q

PYR test

P-naphthylamide + p-dimethylaminocinnamaldehyde
(PYRase)
→

A

Pink color

46
Q

GAS

SEROLOGICAL TEST:

A

• ASO (anti-streptolysin 0)
• Sero typing of specific M CHON

47
Q

SCARLET FEVER SUSCEPTIBILITY TESTS

A
  1. DICK TEST
  2. SCHULTZ-CHARLTON TEST
48
Q

• 0.1ml toxin (test arm) & 0.1ml toxoid (control arm)
• Observe for 24 hrs.
• (+) redness in test arm (1 cm)
• Susceptible to scarlet fever

A

DICK TEST

49
Q

: (blanching phenomenon)
• Inject 0.1 mL of anti-toxin subcutaneously
• (+) fadind o redness after 6 to 8 hours
• Neutralization of erythrogenic toxin

A

SCHULTZ-CHARLTON TEST

Bacte LEC (51 decks)

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