Genus Streptococcus

• What is the Gram stain result for Streptococci?

  Gram positive
• What is the catalase result for Streptococci?

  Catalase negative
• What type of pathogens are Streptococci?

  Pathogenic, opportunistic, and commensal saprophytes
• How are Streptococci classified?

  • Based on haemolytic properties:
  • Alpha-Haemolytic: green on blood agar
  • Beta-Haemolytic: clear areas on blood agar
  • Gamma-Haemolytic: no haemolysis
• What color do alpha-haemolytic species turn on blood agar?

  Green
• Which species are classified as alpha-haemolytic?

  Pneumococci and Viridans
• What is the characteristic of beta-haemolytic Streptococci?

  Complete rupture of RBCs
• How many Lancefield groups are there for beta-haemolytic Streptococci?

  20 groups (A-V)
• What is the characteristic of gamma-haemolytic Streptococci?

  No haemolysis occurs
• Which species are classified as gamma-haemolytic?

  Enterococci
• What is a general feature of S. Pneumoniae and S. Viridans?

  Both are alpha-haemolytic
• What shape do S. Pneumoniae bacteria have?

  Lancet-shaped diplococci
• What is the oxygen requirement for S. Pneumoniae?

  Facultative anaerobe
• What are the virulence factors of S. Pneumoniae?

  Capsule, IgA protease, teichoic acid, pneumolysin O
• What is the primary reservoir for S. Pneumoniae?

  Human upper respiratory tract
• How is S. Pneumoniae transmitted?

  Respiratory droplets
• What are the predisposing factors for S. Pneumoniae infections?

  COPD, alcoholism, influenza, chronic heart failure
• What is the clinical presentation of S. Pneumoniae infection?

  Lobar pneumonia with rusty-colored sputum
• What is the first-line treatment for S. Pneumoniae meningitis?

  Ceftriaxone or Cefotaxime
• What vaccine is used for adults against S. Pneumoniae?

  23-valent polysaccharide vaccine
• What is the purpose of the Quellung reaction in diagnosing S. Pneumoniae?

  To detect capsular polysaccharide
• What is the morphology of S. Viridans?

  Spherical or ovoid shape
• What is the primary reservoir for S. Viridans?

  Human oropharynx
• What are the clinical presentations of S. mutans?

  Dental caries and infective endocarditis
• What are the symptoms of infective endocarditis caused by S. Viridans?

  Malaise, anorexia, night sweats, weight loss
• What is the treatment for infective endocarditis caused by S. Viridans?

  Penicillin G with aminoglycosides
• What is the morphology of S. Pyogenes?

  Coccal shape
• What is the Gram stain result for S. Pyogenes?

  Gram positive
• What is the virulence factor of S. Pyogenes that inhibits complement activation?

  M-protein
• What are the clinical manifestations of S. Pyogenes infections?

  Impetigo, pharyngitis, cellulitis
• What is the relationship between S. Pyogenes and rheumatic fever?

  M-protein mimics cardiac myosin
• What is the treatment for S. Pyogenes infections?

  Penicillin
• What is the morphology of S. Agalactiae?

  Chain-like arrangement
• What is the primary reservoir for S. Agalactiae?

  Genital and GI tract
• What is the clinical manifestation of S. Agalactiae in newborns?

  Neonatal meningitis
• What is the treatment for S. Agalactiae infections?

  Penicillin
• What is the morphology of Enterococci?

  Diplococci
• What is the primary clinical manifestation of Enterococci?

  Urinary tract infections
• What is the treatment for vancomycin-resistant Enterococcus (VRE)?

  Linezolid or Daptomycin
• What are the key features of Enterococci?

  • Gamma-haemolytic
  • PYR positive
  • Growth in bile and 6.5% NaCl
  • Two species: E. faecium & E. faecalis