Streptococcus agalactiae (Group B Streptococci)

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

Studies

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