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STREPTOCOCCI

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hemolysis reaction - sheep blood agar (alpha) partial hemolysis. green color (beta) ... black precipitate. 6.5% saline. grow. enterococci. no growth. non ... – PowerPoint PPT presentation

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Title: STREPTOCOCCI


1
STREPTOCOCCI
Faculty Dr. Alvin Fox
2
Key Words
  • Group B streptococcus (S.agalactiae)
  • Neonatal septicemia/meningitis
  • CAMP test
  • Hippurate hydrolysis test
  • Group D streptococcus
  • Urinary tract infection/ endocarditis
  • Bile-esculin test
  • Enterococci
  • Non-enterococci
  • Large colony
  • Minute colony
  • Viridans streptococci
  • Dental caries/endocarditis
  • Lancefield groups
  • Hemolysis (alpha, beta, gamma)
  • Group A streptococcus (S. pyogenes)
  • Bacitracin susceptibility test
  • M, T, R proteins
  • Streptolysins O and S
  • F protein/lipoteichoic acid
  • Rheumatic fever/carditis/arthritis
  • Glomerulonephritis
  • Scarlet fever
  • Toxic shock-like syndrome/bacteremia
  • Flesh-eating bacteria
  • Pyrogenic toxin
  • Erythrogenic toxin

3
  • Streptococci
  • facultative anaerobe
  • Gram-positive
  • chains or pairs
  • catalase negative
  • (staphylococci are catalase positive)

4
Streptococcus in chains (Gram stain)
5
Streptococcus pneumoniae (diplococcus).
Fluorescent stain
6
  • Streptococci
  • Lancefield groups
  • one or more species per group
  • surface antigens

7
groupable streptococci
  • A, B and D
  • most important
  • C, G, F
  • rare

8
Non-groupable
  • S. pneumoniae
  • pneumonia
  • viridans streptococci
  • e.g. S. mutans
  • dental caries

9
hemolysis reaction - sheep blood agar
  • ? (alpha)
  • partial hemolysis
  • green color
  • ? (beta)
  • complete clearing
  • A and B
  • ? (gamma)
  • no lysis

White colonies
10
Hemolysis
  • Groups A an B
  • ?
  • Group D
  • ? or ?
  • S. pneumoniae and viridans
  • ?

11
  • hemolysis reaction one characteristic
  • presumptive identification

12
Group A streptococcus (S. pyogenes)
13

Group A streptococcal infections affect all
ages peak incidence at 5-15 years of age
14
S. pyogenes -suppurative
  • non-invasive
  • pharyngitis
  • skin infection, impetigo
  • invasive bacteremia
  • toxic shock-like syndrome
  • "flesh eating" bacteria
  • pyrogenic toxin

15
Pyrogenic toxin
  • superantigen
  • T cell mitogen
  • activates immune system

16
Scarlet fever
  • rash
  • erythrogenic toxin

17
non-suppurative
  • rheumatic fever
  • inflammatory disease
  • life threatening
  • chronic sequalae
  • fever
  • heart
  • joints
  • rheumatic NOT rheumatoid arthritis

18
Rheumatic fever -etiology
  • M protein
  • cross-reacts heart myosin
  • autoimmunity
  • Cell wall antigens
  • poorly digested in vivo
  • persist indefinitely

19
Rheumatic fever
  • penicillin
  • terminates pharyngitis
  • decreases carditis

20
Acute glomerulonephritis
  • immune complex disease of kidney

21
Major pathogenesis factors
  • lipoteichoic acid/F protein
  • fimbriae
  • binds to epithelial cells
  • M protein
  • anti-phagocytic

22
S. pyogenes
lipoteichoic acid F-protein
fibronectin
epithelial cells
23
M protein
IMMUNE
Complement
IgG
M protein
NON-IMMUNE
peptidoglycan
fibrinogen
24
M protein
  • major target
  • natural immunity
  • strain variation
  • antigenicity
  • re-infection
  • occurs with different strain

25
Capsules
  • Anti-phagocytic
  • mucoid strains

26
Isolation and identification
  • ? hemolytic colonies
  • bacitracin inhibits growth
  • ? hemolytic colonies
  • group A antigen

27
? hemolysis
  • hemolysin O
  • sensitive oxygen
  • hemolysin S
  • insensitive oxygen

28
Another Rapid Strep Test
Throat swab extract (/- streptococcal antigen)
-

Antibody
Liposome
Streptococcal antigen
29
Post-infectious diagnosis (serology)
  • antibodies to streptolysin O
  • important if delayed clinical sequelae occur

30
Typing
Traditional serotyping of proteins - M - T - R
Modern - Sequencing of M protein gene
31
Group B streptococcus
  • neonatal meningitis
  • septicemia
  • transmission
  • vaginal flora

32
Group B streptococcus - identification
  • ? hemolysis
  • hippurate hydrolysis
  • CAMP reaction
  • increases ? hemolysis of S. aureus

33
Group D streptococcus
  • Growth on bile esculin agar
  • black precipitate
  • 6.5 saline
  • grow
  • enterococci
  • no growth
  • non-enterococci

34
Enterococci
  • distantly related to other streptococci
  • genus Enterococcus
  • gut flora
  • urinary tract infection
  • fecal contamination
  • opportunistic infections
  • particularly endocarditis
  • most common E. (S.) faecalis

35
Enterococci
  • resistant to many antibiotics
  • including vancomycin
  • terminal D-ala replaced by D-lactate

36
Minute colony streptococci
  • Various groups/hemolysis (e.g. group A)
  • genetically distinct
  • from large colony (e.g. S. pyogenes)
  • no rheumatic fever

Large colony
Minute colony
37
Viridans streptococci
  • diverse species
  • oral
  • dental caries
  • ? hemolytic and negative for other tests
  • non-groupable.
  • includes S. mutans
  • endocarditis
  • tooth extraction
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