Updated: 1/21/2019

Streptococcus agalactiae (Group B Streptococci)

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  • A 29-year-old woman at 36-weeks gestation presents to her obstetrician for a prenatal visit. She denies any bloody vaginal fluid production and endorses the presence of spontaneous fetal movement. Ultrasonography demonstrates infant size that is appropriate for gestational age. She undergoes a rectal and vaginal swab, which grows group B streptococci. Preparations are made to receive intrapartum penicillin G prophylaxis.
  • Classification
    • gram-positive cocci that are
      • β-hemolytic 
      • produces CAMP factor
        • an extracellular substance produced by that enlarges the area of hemolysis formed by Staphylococcus aureus
      • catalase-negative
      • facultative anaerobe
      • bacitracin resistant
      • hippurate test positive
      • PYR negative
  • Reservoir
    • vagina and gastrointestinal tract
  • Prevention
    • at 35-37 weeks gestation, a rectal and vaginal swab is performed to determine the presence of group B streptococcus (GBS)
      • if the cultures return positive for GBS, patients receive intrapartum penicillin G or ampicillin prophylaxis
  • Pathogenesis
    • infection occurs in utero secondary to
      • intraamniotic infection
      • rupture of membranes
      • passage through the vagina
  • Associated conditions
    • neonatal meningitis
    • neonatal sepsis
    • neonatal pneumonia
  • Symptoms/physical exam
    • neonatal septicemia
      • irritability
      • lethargy
      • respiratory distress (e.g., tachypnea, hypoxia, and grunting)
    • neonatal meningitis
      • irritability
      • lethargy
      • respiratory distress (e.g., tachypnea, hypoxia, and grunting)
      • poor feeding and vomiting
      • bulging fontanel
      • nuchal rigidity
    • neonatal pneumonia
      • respiratory distress (e.g., tachypnea, hypoxia, and grunting)
        • patients will have a diffuse alveolar pattern on chest radiography
  • GBS isolation from a sterile body site (e.g., blood and cerebrospinal fluid)
  • Neonatal meningitis by other organisms (e.g., E. coli and L. monocytogenes)
    • differentiating factors
      • E. coli
        • gram-negative
      • L. monocytogenes
        • gram-positive rod
  • Medical
    • penicillin G
      • indication
        • treatment of choice after GBS has been confirmed to be the only organism causing infection in the neonate and infant

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