What is the treatment for group B strep (Streptococcus agalactiae) colonization during pregnancy?

Treatment for Group B Streptococcus During Pregnancy

Pregnant women with Group B Streptococcus (GBS) colonization should receive intrapartum antibiotic prophylaxis with intravenous penicillin G (5 million units IV initial dose, followed by 2.5 million units IV every 4 hours until delivery) to prevent early-onset neonatal GBS disease. 1

Screening and Identification

• All pregnant women should be screened for GBS colonization at 35-37 weeks' gestation with vaginal-rectal cultures 2
• Screening involves collection of a single swab or two separate swabs from the distal vagina and rectum (not by speculum examination) 2
• Specimens should be placed in transport medium if the laboratory is offsite and specifically identified for GBS culture 2

Indications for Intrapartum Antibiotic Prophylaxis

Intrapartum antibiotic prophylaxis is indicated in the following situations:

• Positive GBS vaginal-rectal screening culture in current pregnancy 2, 1
• GBS bacteriuria during any trimester of current pregnancy 2, 1
• Previous infant with invasive GBS disease 2, 1
• Unknown GBS status at labor onset with any of the following risk factors:
  • Delivery at <37 weeks' gestation
  • Amniotic membrane rupture ≥18 hours
  • Intrapartum temperature ≥100.4°F (≥38.0°C) 2

Antibiotic Regimens

First-line therapy:

• Penicillin G: 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery 2, 1

Alternative regimens:

• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery 2, 1
  • Note: Penicillin G is preferred due to its narrower spectrum 2

For penicillin-allergic women:

• Non-anaphylactic allergy: Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours until delivery 1
• Anaphylactic allergy: Clindamycin (if isolate is susceptible) 2, 1
  • Note: Erythromycin is no longer recommended due to increasing resistance and poor placental transfer 1

Important Considerations

• Intrapartum antibiotics should be administered as early as possible during labor for maximum effectiveness, ideally at least 4 hours before delivery 1, 3
• Oral antibiotics during pregnancy are NOT effective for eliminating GBS colonization or preventing neonatal disease 2, 1
• Treatment of GBS bacteriuria during pregnancy should follow standard UTI treatment protocols, but intrapartum prophylaxis is still required during labor 1
• Intrapartum antibiotic prophylaxis is not indicated for cesarean delivery performed before labor onset on a woman with intact amniotic membranes, regardless of GBS status 2

Effectiveness and Safety

• Intrapartum antibiotic prophylaxis reduces the risk of early-onset neonatal GBS infection from approximately 4.7% to 0.4% 4
• The main risk of penicillin therapy is anaphylactic reaction (approximately 5 cases per 10,000 treatments) 4
• Implementation of GBS screening and prophylaxis guidelines has been associated with significant decline in early-onset neonatal GBS infections 4

Following these evidence-based guidelines for GBS screening and prophylaxis is crucial for preventing early-onset neonatal GBS disease, which remains a significant cause of neonatal morbidity and mortality.