GBS in Pregnancy: Prophylaxis and Treatment
For pregnant women, the goal is not to permanently eliminate the GBS bacteria, which can recolonize, but to prevent transmission to the baby during birth. The standard of care involves screening and, if necessary, administering antibiotics during labor.
Intrapartum Antibiotic Prophylaxis (IAP)
IAP is the most effective strategy for preventing early-onset GBS disease in newborns.
- Screening: All pregnant women are typically screened for GBS colonization via a vaginal and rectal swab between 36 and 37 weeks of pregnancy. A positive result indicates the need for IAP.
- Timing is Critical: Intravenous (IV) antibiotics are administered during labor, ideally starting at least four hours before delivery. Taking oral antibiotics earlier in the pregnancy is not effective for preventing transmission at birth because the bacteria can regrow quickly.
- Standard Antibiotics: Penicillin G is the preferred antibiotic for IAP, with ampicillin as an acceptable alternative.
Other Scenarios Requiring Antibiotics in Pregnancy
Antibiotics are also recommended during labor if the mother has any of the following risk factors, even without a positive GBS screening result at 36-37 weeks:
- Preterm labor (before 37 weeks' gestation) with unknown GBS status.
- Prolonged rupture of membranes (18+ hours).
- Fever during labor.
- A positive GBS urine culture at any point during the current pregnancy.
- History of a previous infant with invasive GBS disease.
GBS Treatment for Neonates
If a newborn develops a GBS infection, immediate and aggressive antibiotic therapy is crucial. Treatment is administered in a neonatal intensive care unit (NICU) and tailored to the type and severity of the infection.
- Empiric Therapy: Initial treatment for suspected neonatal sepsis often includes both ampicillin and an aminoglycoside, such as gentamicin, to ensure broad coverage.
- Targeted Therapy: Once GBS is confirmed, penicillin G is often used as the preferred agent.
- Duration: A 10-day course of intravenous antibiotics is typical for uncomplicated bacteremia, while more severe infections like meningitis may require at least 14 days or longer.
GBS Treatment for Non-Pregnant Adults
While GBS is most known for affecting newborns, it can also cause serious infections in adults, particularly those with underlying conditions like diabetes, cancer, or advanced age.
- Standard Treatment: Penicillin G remains the antibiotic of choice for invasive GBS disease in adults.
- Alternative Therapies: For patients with penicillin allergies, alternatives include vancomycin or cephalosporins, depending on the severity of the allergy and the location of the infection.
- Duration: The duration of treatment depends on the site of infection. For example, bacteremia may require 10 days, while meningitis could need a minimum of 14 days.
- Surgical Intervention: For severe infections, such as those involving soft tissue, bone, or heart valves, surgery may be required in addition to antibiotics.
Managing Penicillin Allergies
For patients with a documented or suspected penicillin allergy, the choice of antibiotic requires careful consideration.
| Allergy Risk Level | Recommended Alternative Antibiotic(s) | Notes |
|---|---|---|
| Low-Risk | Cefazolin | A first-generation cephalosporin often used for prophylaxis in pregnant women with a mild, non-anaphylactic penicillin allergy. |
| High-Risk | Clindamycin or Vancomycin | For women with a history of severe reactions (e.g., anaphylaxis, hives). Antibiotic susceptibility testing of the GBS isolate is crucial for guiding this choice, as resistance to clindamycin is increasing. |
Limitations and Future Directions
Antibiotics are highly effective but have limitations. The widespread use of IAP has raised concerns about antibiotic resistance. Researchers are actively working on developing a maternal vaccine to prevent GBS infections. A vaccine could help reduce reliance on antibiotics and potentially prevent both early- and late-onset GBS disease. Currently, there is no effective strategy to prevent late-onset GBS disease in infants (occurring after the first week of life) or disease in non-pregnant adults.
For more information on GBS prevention and guidelines, consult the Centers for Disease Control and Prevention at https://www.cdc.gov/group-b-strep/.
Conclusion
In summary, antibiotic therapy is the established and most effective method for managing Group B strep infections. In pregnant women, intravenous antibiotics administered during labor are critical for preventing newborn infection. For infants and non-pregnant adults, the specific antibiotic and duration of treatment depend on the infection's location and severity. While penicillin is the first-line choice, alternatives are available for those with allergies. While challenges like antibiotic resistance and the prevention of late-onset disease persist, ongoing research into vaccines offers a promising path forward for reducing the burden of GBS.
