strep & entero

• What type of bacteria are Streptococci and Enterococci?

  Catalase negative
• What type of bacteria are Staphylococci and Micrococci?

  Catalase positive
• What family do Streptococcus spp. belong to?

  Streptococcaceae
• What is the Gram stain result for Streptococcus spp.?

  Gram (+) cocci in pairs and chains
• How do Streptococci appear under a microscope compared to Staphylococci?

  Streptococci appear elongated in chains
• What is the aerotolerance of Streptococci?

  Facultative anaerobes, aerotolerant anaerobes, capnophilic
• What is a capnophile?

  Requires >5-10% carbon dioxide
• Can Streptococci ferment glucose, and do they produce gas?

  Yes, but no gas is produced
• How do Streptococci colonies appear on agar?

  Small and transparent
• What are the classifications of Streptococci based on hemolytic reactions?

  • β-hemolytic: clear zone, complete lysis
  • α-hemolytic: greenish zone, partial lysis
  • Nonhemolytic: no color change, no lysis
• What is the serologic specificity of Streptococci determined by?

  An amino sugar in the cell wall
• What are the group antigens for Streptococci and their carbohydrate content?

  • Group A: rhamnose-N-acetylglucosamine
  • Group B: rhamnose-glucosamine polysaccharide
  • Group C: rhamnose-N-acetylgalactosamine
  • Group D: glycerol teichoic acid
  • Group F: glucopyranosyl-N-acetylgalactosamine
• What is the significance of the hemolytic pattern in Streptococci?

  It indicates the type of lysis of RBCs
• What is the role of exotoxins in Streptococci?

  They damage intact RBCs as a virulence factor
• What are the descriptions of hemolytic patterns in Streptococci?

  • β-hemolytic: complete lysis, clear area
  • α-hemolytic: partial lysis, greening
  • γ-hemolytic: no lysis, no change
• Who developed the Lancefield classification?

  Rebecca Lancefield
• What is the common disease association with Group A Streptococcus (S. pyogenes)?

  Rheumatic fever and pharyngitis
• What is the hemolytic pattern of S. agalactiae (Group B)?

  β-hemolytic
• What is the disease association with S. pneumoniae?

  Pneumonia and meningitis
• Why does S. pneumoniae not have a Lancefield classification?

  It lacks antigens and C carbohydrate
• What are the characteristics of Viridans streptococci?

  • Usually α-hemolytic
  • Group name, not a genus or species
  • Capable of presenting α-hemolytic pattern
• What is the current terminology for nonhemolytic patterns in Streptococci?

  Nonhemolytic pattern instead of gamma
• What is the classification of Enterococcus spp.?

  Previously under Streptococci, now reclassified
• What are the antigen characteristics of Streptococci according to Mahon?

  • Generally acid labile except Antigen B
  • Antigen B is acid stable
  • Other antigens are acid labile
• Where is Streptococcus pyogenes commonly found?

  Upper respiratory tract
• What are the virulence factors of Streptococcus pyogenes?

  • M protein: resists phagocytosis
  • Protein F: adheres to epithelial cells
  • Hyaluronic acid capsule: impedes phagocytosis
  • Streptolysins O and S: lyse RBCs
• What is the function of Streptolysin O?

  Lyses RBC anaerobically
• What is the function of Streptolysin S?

  Lyses RBC aerobically
• What are the differences between Streptolysin O and S?

  • O: anaerobic, highly immunogenic
  • S: aerobic, non-immunogenic
• What is the role of deoxyribonuclease (DNase) in Streptococcus pyogenes?

  Interferes with phagocytosis and spreads infection
• What is the function of streptokinase?

  Lyses fibrin clots to escape infections
• What does hyaluronidase do?

  Hydrolyzes hyaluronic acid in connective tissue
• What are streptococcal pyrogenic exotoxins also known as?

  Erythrogenic toxins
• What is the effect of streptococcal pyrogenic exotoxins?

  Causes a red spreading rash (scarlet fever)
• How can hemolysis of RBC be observed in BAP?

  By making a pit in the agar for SLO
• What is the significance of streptolysin S in hemolysis?

  It shows beta-hemolytic pattern on the surface
• What is the immunogenicity of streptolysin O?

  Highly immunogenic, triggers immune response
• What does streptolysin O serve as?

  An antigen that initiates immune response
• What are the different classes of streptococcal pyrogenic exotoxin?

  SpeA, SpeB, SpeC, and SpeF
• How can hemolysis of RBC be observed in BAP?

  It can be seen in the subsurface