Efficacy of intramuscular penicillin in the eradication of group B streptococcal colonization at delivery

J Matern Fetal Neonatal Med. 2005 May;17(5):333-5. doi: 10.1080/14767050500132302.


Objective: Due to rapid deliveries and human error, not all group B streptococcal positive mothers will receive adequate prophylactic antibiotic treatment in labor. We sought to determine if long acting intramuscular penicillin given after a positive culture result would be efficacious in eradicating group B streptococcal colonization at the time of delivery.

Methods: Patients positive for group B streptococci at 35-37 weeks were randomized to receive 2.4 million units of intramuscular benzathine penicillin G suspension (Bicillin L-A) versus no treatment. Study patients were recultured at the time of admission to labor and delivery prior to receiving prophylactic antibiotics according to CDC guidelines.

Results: A total of 53 patients were enrolled. A small but significant decrease in the rate of group B streptococcal colonization was observed in the treatment group (14/27, 52%) versus the control group (20/23, 87%), p=0.03.

Conclusion: The large number of persistent carriers suggests that 2.4 million units of intramuscular benzathine penicillin G suspension (Bicillin L-A) is insufficient as sole therapy. However, the decline in group B streptococcal carriers might lessen the risk of failed or insufficient intrapartum treatment. Intramuscular benzathine penicillin G suspension (Bicillin L-A) may be useful as an adjunctive treatment for patients at risk for rapid delivery, before adequate intrapartum prophylaxis can be given.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-Bacterial Agents / administration & dosage*
  • Colony Count, Microbial
  • Delivery, Obstetric*
  • Female
  • Humans
  • Injections, Intramuscular
  • Penicillin G Benzathine / administration & dosage*
  • Pregnancy
  • Pregnancy Complications, Infectious / drug therapy*
  • Prenatal Care / methods
  • Prospective Studies
  • Streptococcal Infections / drug therapy*
  • Streptococcus agalactiae*
  • Treatment Outcome


  • Anti-Bacterial Agents
  • Penicillin G Benzathine