strep & entero (iso & iden)

• What type of bacteria are streptococci?

  Gram positive cocci
• How do streptococci typically appear under a microscope?

  Singly or in pairs, often in long chains
• What is the aerotolerance of streptococci?

  Facultative anaerobe
• What is the motility characteristic of streptococci?

  Generally non-motile
• What type of infections do pyogenic bacteria cause?

  Pyogenic infections
• What are the classifications of Streptococcus and Enterococcus based on Lancefield's system?

  • Group A: S. pyogenes
  • Group B: S. agalactiae
  • Group C: S. dysgalactiae & S. equi
  • Group D: S. bovis group and Enterococcus
  • S. pneumoniae
  • Viridans streptococci
• What disease is associated with S. pyogenes?

  Rheumatic fever
• What is the hemolysis type of S. agalactiae?

  Beta hemolysis
• What infections are caused by S. agalactiae?

  Neonatal sepsis and meningitis
• How can S. dysgalactiae be differentiated from other beta-hemolytic streptococci?

  Resistance to bacitracin and negative CAMP test
• What is the hemolytic pattern of S. pneumoniae?

  Alpha hemolysis
• What is a significant characteristic of virulent strains of S. pneumoniae?

  Covered with polysaccharide capsule
• What is the presumptive identification test for S. pneumoniae?

  Positive optochin susceptibility test
• What is the appearance of viridans streptococci on blood agar?

  Very small, gray to whitish gray colonies
• What is the primary habitat of Group D enterococci?

  Gastrointestinal tract
• What infections can enterococci cause?

  Urinary tract infections and endocarditis
• What is the hemolytic pattern of E. faecalis?

  Nonhemolytic or beta-hemolytic
• What is the key reaction for S. bovis?

  Positive bile esculin test
• What is the appearance of Group A streptococci on blood agar?

  Large zone of beta-hemolysis
• What does a negative catalase test indicate?

  Organism is catalase negative
• What is the purpose of the optochin susceptibility test?

  • Determines effect of optochin on organisms
  • Identifies Streptococcus pneumoniae
  • Positive test: lysis of pneumococci
  • Negative test: resistance in alpha-streptococci
• What is the expected result for a positive optochin test?

  Zone of inhibition at least 14 mm
• What does the bile solubility test differentiate?

  Streptococcus pneumoniae from alpha-hemolytic streptococci
• What is the principle behind the bile solubility test?

  Bile lyses pneumococcal colonies
• What is the expected result for a positive bile solubility test?

  Colony disintegrates
• What is the purpose of the bile esculin test?

  Presumptive identification of enterococci
• What does a positive bile esculin test indicate?

  Presence of enterococci or Group D streptococci
• What is the appearance of Group C streptococci on blood agar?

  Grayish white with wide zone of hemolysis
• What is the significance of the CAMP test for Group B streptococci?

  Preliminary identification of S. agalactiae
• What is the typical colony morphology of S. pneumoniae?

  Smooth and mucoid
• What is the role of the optochin disk in the susceptibility test?

  To inhibit growth of susceptible organisms
• How does the appearance of viridans streptococci differ from pneumococci on blood agar?

  Viridans are smaller and grayish
• What is the typical hemolytic pattern of Group D non-enterococci?

  Nonhemolytic or alpha-hemolytic
• What is the significance of the salt broth test for Group D streptococci?

  To differentiate from enterococci
• What is the expected result for a negative bile solubility test?

  Intact colonies
• What is the appearance of colonies for S. bovis?

  Large and mucoid
• What is the typical growth condition for cultures in the optochin susceptibility test?

  Incubated at 35°C in 5% CO2
• What is the significance of the CAMP reaction for Group B streptococci?

  It helps in preliminary identification
• How does the identification of S. pneumoniae differ from other streptococci?

  It requires optochin susceptibility testing
• What is the appearance of colonies for E. faecium?

  Alpha-hemolytic