Vaginal group B streptococcus status during intrapartum antibiotic prophylaxis

Int J Gynaecol Obstet. 2015 Apr;129(1):9-12. doi: 10.1016/j.ijgo.2014.10.018. Epub 2014 Dec 18.


Objective: To assess maternal group B streptococcus (GBS) colonization status and the pharmacokinetic profile of penicillin G in the umbilical cord and amniotic fluid compartment during 4 hours of intrapartum antibiotic prophylaxis (IAP).

Methods: In a prospective study at a hospital in Montevideo, Uruguay, 60 GBS carriers in active labor after a singleton pregnancy of 37 weeks or more were enrolled between April 1, 2011, and April 30, 2012. Intravenous penicillin G was administered via a standard regimen. Rectovaginal samples were obtained before IAP initiation, and 2 and 4 hours after the initial dose. Penicillin G concentrations were measured by high-performance liquid chromatography. Samples were obtained from fetal cord blood in all cases and from amniotic fluid obtained from patients who delivered by cesarean.

Results: Among the 60 participants, 43 (72%) had a positive rectovaginal sample before IAP initiation. Of these women, 23 (53%) had negative cultures after 2 hours; after 4 hours, only 5 (12%) remained positive for GBS. The penicillin G concentration in amniotic fluid and cord blood was above the minimum inhibitory concentration (0.12 μg/mL) in all cases.

Conclusion: Four hours of IAP was needed to reduce the number of women with positive GBS cultures to 12%. Therefore, 4 hours of IAP might be necessary to achieve overall effectiveness from this treatment.

Keywords: Group B streptococcus; Intrapartum antibiotic prophylaxis; Penicillin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amniotic Fluid / metabolism
  • Anti-Bacterial Agents / administration & dosage*
  • Anti-Bacterial Agents / analysis
  • Antibiotic Prophylaxis / methods*
  • Carrier State
  • Female
  • Fetal Blood / chemistry
  • Humans
  • Infectious Disease Transmission, Vertical / prevention & control
  • Penicillin G / administration & dosage*
  • Penicillin G / analysis
  • Pregnancy
  • Pregnancy Complications, Infectious / prevention & control
  • Prospective Studies
  • Rectum / microbiology*
  • Streptococcal Infections / prevention & control
  • Streptococcal Infections / transmission
  • Streptococcus agalactiae / drug effects*
  • Streptococcus agalactiae / isolation & purification
  • Time Factors
  • Umbilical Cord / metabolism
  • Vagina / microbiology*
  • Young Adult


  • Anti-Bacterial Agents
  • Penicillin G