Efficacy of intramuscular penicillin in the eradication of group Bstreptococcal colonization at delivery

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The Journal of Maternal-Fetal & Neonatal Medicine


IM penicillin, group B streptococcal prophylaxis


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.