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Updated: Mar 31 2022

Streptococcus agalactiae (Group B Streptococci)

Images
https://upload.medbullets.com/topic/104031/images/streptococcus classification - moises.jpg
https://upload.medbullets.com/topic/104031/images/streptococcus_agalactiae_on_blood_agar.jpg
  • Snapshot
    • 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.
  • Introduction
    • 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
  • Presentation
    • 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
  • Studies
    • GBS isolation from a sterile body site (e.g., blood and cerebrospinal fluid)
  • Differential
    • Neonatal meningitis by other organisms (e.g., E. coli and L. monocytogenes)
      • differentiating factors
        • E. coli
          • gram-negative
        • L. monocytogenes
          • gram-positive rod
  • Treatment
    • 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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