What is the treatment approach for group B strep (Group B Streptococcus) colonization in pregnant women?

From the Guidelines

The treatment approach for Group B Streptococcus (GBS) colonization in pregnant women involves intrapartum antibiotic prophylaxis rather than oral antibiotics, as oral antibiotics alone are not adequate for GBS prophylaxis 1.

Key Considerations

• Women who test positive for GBS during routine screening at 36-37 weeks gestation should receive antibiotics during labor to prevent transmission to the newborn.
• The recommended first-line antibiotic is intravenous penicillin G with an initial dose of 5 million units, followed by 2.5-3 million units every 4 hours until delivery.
• For women with penicillin allergy without anaphylaxis risk, cefazolin 2g initial dose followed by 1g every 8 hours is recommended.
• If at high risk for anaphylaxis, clindamycin 900mg every 8 hours or vancomycin 20mg/kg every 8 hours (if GBS is resistant to clindamycin) should be administered.

Rationale

Antibiotics should be started at the onset of labor or rupture of membranes and continued until delivery, as this approach provides adequate antibiotic levels in the amniotic fluid and fetal circulation during the critical period of potential transmission, significantly reducing the risk of early-onset GBS disease in newborns 1.

Important Notes

• GBS colonization during pregnancy itself is not treated as it represents normal flora that often returns even after treatment, making intrapartum prophylaxis the most effective strategy.
• The guidelines from the CDC, as outlined in the 2010 revised guidelines, emphasize the importance of intrapartum antibiotic prophylaxis for preventing perinatal GBS disease 1.

From the Research

Treatment Approach for Group B Strep Colonization in Pregnant Women

The treatment approach for group B strep (Group B Streptococcus) colonization in pregnant women typically involves intrapartum antibiotic prophylaxis (IAP) to prevent the transmission of the bacteria to the newborn during delivery.

• The American Academy of Pediatrics and the American College of Obstetricians and Gynecologists recommend maternal intrapartum antibiotic prophylaxis based on antenatal screening for GBS colonization as the primary approach to prevent perinatal GBS disease 2.
• Penicillin, ampicillin, or cefazolin are recommended for prophylaxis, with clindamycin and vancomycin reserved for cases of significant maternal penicillin allergy 2.
• The optimal window for screening is between 36 0/7 to 37 6/7 weeks of gestation, rather than beginning at 35 0/7 weeks' gestation 2.
• Intrapartum antibiotic prophylaxis has been shown to be highly effective in preventing early-onset GBS disease, with a reduction in incidence from 1.8 cases/1000 live births in the early 1990s to 0.26 cases/1000 live births in 2010 3.
• The use of IAP has been associated with a reduced incidence of early GBS infection, with a risk ratio of 0.17 (95% confidence interval 0.04 to 0.74) compared to no treatment 4.

Oral Antibiotics for Group B Strep

There is limited information available on the use of oral antibiotics for group B strep colonization in pregnant women.

• The studies reviewed primarily discuss the use of intravenous antibiotic prophylaxis during labor, rather than oral antibiotics 5, 2, 3, 4, 6.
• Clindamycin is sometimes used as an alternative to penicillin or ampicillin for women with a penicillin allergy, but its effectiveness is lower than that of penicillin or ampicillin 6.
• There is no clear evidence to support the use of oral antibiotics as a primary treatment approach for group B strep colonization in pregnant women.

Key Considerations

When considering the treatment approach for group B strep colonization in pregnant women, several key factors should be taken into account.

• The risk of early-onset GBS disease is higher in certain situations, such as preterm delivery, maternal fever during delivery, and membrane rupture more than 18 hours before delivery 5.
• The effectiveness of IAP can be influenced by the duration of prophylaxis, with longer durations (4 or more hours) being more effective than shorter durations 6.
• The choice of antibiotic should be based on the mother's allergy history, with penicillin or ampicillin being the preferred options for women without a penicillin allergy 2.