Strep agalactiae

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Streptococcus agalactiae

  • Also known as Group B streptococcus
  • Characteristics
    • Gram + cocci
    • Catalase negative
      • First-test; determines staph (catalase positive) vs. strep 
    • Beta-hemolytic
      • Second test; determines subtype of strep or enterococci
    • PYR – 
      • Third test; used to rule out strep pyogenes (PYR+)
    • Bacitracin-resistant
      • Third test; also used to rule out strep pyogenes (PYR+), although bacitracin is not specific so it is less commonly used than PYR.
    • Produces CAMP factor = enlarges hemolysis by S aureus
      • CAMP stands for Christie-Atkins-Munch-Peterson
        • Note: this is NOT cAMP!! 
      • CAMP factor synergistically enhances action of beta-lysin produced by S. aureus, to increase area of hemolysis
    • Hippurate test +
    • Facultative anaerobe 
  • Presentation
    • Part of normal gastrointestinal and urogenital flora
    • pneumonia, meningitis, and sepsis
      • mainly in neonates
      • Transmitted during vaginal delivery from mother to neonates
    • Screen and Treat pregnant moms at 35-37 weeks of gestation
      • Using rectal and vaginal swabs
      • If positive → prophylaxis with penicillin
  • Treatment
    • Penicillin G
      • Penicillin G is the antibiotic of choice for this organism in both the colonized mother and the infected infant