Streptococcus and Enterococci: Isolation and Identification

• Streptococci differs from staphylococci in 2 significant characteristics:

  1. Long chains
  2. Lack catalase enzyme
• Streptococci is

  • Gram positive cocci
  • Facultative anaerobe
  • Non motile
  • Some are capnophilic
  • Pyogenic causing bacteria
• S. pyogenes

  LF group: A

  Hemolysis type: Beta

  Term: Group A streptococci

  Diseases:

  • Rheumatic fever
  • Scarlet fever
  • Pharyngitis
  • Glomerulonephritis
  • Pyogenic infection
• S. agalactiae

  LF group: B

  Hemolysis type: Beta

  Term: Group B streptococci

  Diseases:

  • Neonatal sepsis
  • Meningitis
  • Puerperal fever
  • Pyogenic infection
• S. dysgalactiae & S. equi

  LF group: C

  Hemolysis type: Beta

  Term: Group C streptococci

  Diseases:

  • pharyngitis
  • impetigo
  • pyogenic infections
• S. bovis group

  LF group: D

  Hemolysis type: alpha, none

  Term: Non enterococcus member of viridans streptococci

  Diseases:

  • Endocarditis
  • UTI
  • Pyogenic infection
• E. faecalis & E. faecium

  LF group: D

  Hemolyisis type: alpha, beta, none

  Term: Enterococcus

  Diseases:

  • UTI
  • Pyogenic infection
• S. pneumoniae

  LF group: none

  Hemolysis type: alpha

  Term: pneumococcus

  Diseases:

  • pneumonia
  • meningitis
  • pyogenic infection
• anginosus, mitis, mutans, salivarius

  LF group: A, C, F, G, N

  Hemolysis type: Beta, alpha, none

  Term: Viridans streptococci

  Diseases:

  • Endocarditis
  • Dental carries
  • Abscesses in various tissues
  • Pyogenic infection
• GROUP A - S. pyogenes

  • Clear zone (2-4× larger than diameter)
  • Spherical in shape
  • Short chains
  • Diff: Bacitracin test
  • B-hemolytic is sensitive to bacitracin
• GROUP A - S. agalactiae

  • Large Colonies w/ narrow zone of beta hemolysis
  • Found in: Pharynx, Skin, Rectum but more likely to be found in genital and intestinal tract of healthy individuals
  • Identification: (+) CAMP test
  • Infection:
  • Neonatal - Sepsis, meningitis
  • Adult -Abscesses, endocarditis, septicemia
• GROUP A - S. dysgalactiae

  • large zone of b hemolysis on blood agar
  • Diff: bacitracin test and (-) CAMP test
  • Infection: Pharyngitis, endocarditis, meningitis (occur in patients with other illnesses)
  • Uncommon human pathogen buy may be zoonoses