From the Guidelines
Penicillin G is the first-line antibiotic treatment for Group B Streptococcus (GBS) in urine during pregnancy, with a recommended regimen of 5 million units IV initial dose, then 2.5–3.0 million units every 4 hours until delivery. For women with penicillin allergy, alternatives include cefazolin (if non-severe allergy) or clindamycin 900 mg IV every 8 hours until delivery (if severe allergy) 1. Treatment is essential because GBS in urine during pregnancy indicates heavy colonization and increases risk of preterm delivery, premature rupture of membranes, and neonatal GBS infection. After treatment, a follow-up urine culture is recommended to confirm clearance. Additionally, women with GBS bacteriuria at any point during pregnancy should automatically receive intrapartum antibiotic prophylaxis during labor, regardless of subsequent negative cultures, as they are considered heavily colonized 1.
Some key points to consider:
- GBS is highly sensitive to penicillins because these antibiotics inhibit cell wall synthesis in the bacteria, making them particularly effective against this gram-positive organism.
- The recommended regimen for penicillin G is 5 million units IV initial dose, then 2.5–3.0 million units every 4 hours until delivery.
- For women with penicillin allergy, cefazolin or clindamycin may be used as alternatives.
- Intrapartum antibiotic prophylaxis is essential for preventing early-onset GBS disease in newborns.
- Women with GBS bacteriuria at any point during pregnancy should receive intrapartum antibiotic prophylaxis during labor, regardless of subsequent negative cultures.
It's also important to note that the guidelines for prevention of perinatal group B streptococcal disease have been updated and revised over the years, with the most recent guidelines recommending universal screening at 35–37 weeks’ gestation for maternal GBS colonization and use of intrapartum antibiotic prophylaxis 1.
From the Research
Group B Streptococcus (GBS) Infection in Pregnancy
- GBS is a leading cause of life-threatening neonatal bacterial infections in developed countries, with mother-to-child transmission occurring during passage through the birth canal 2.
- The risk of early neonatal GBS infection increases in cases of preterm delivery, maternal fever during delivery, and membrane rupture more than 18 hours before delivery 2.
Antibiotic Prophylaxis for GBS Infection
- Penicillin G (benzylpenicillin) is the antibiotic of choice for preventing early-onset neonatal GBS infection, while penicillin A (ampicillin or amoxicillin) is an alternative 2, 3.
- For women with a penicillin allergy, erythromycin or clindamycin are generally active against Group B streptococci and carry no particular risks for the infant 2.
- Cefazolin and vancomycin are also recommended for prophylaxis in cases of significant maternal penicillin allergy 3, 4.
Management of GBS Positive Urine Culture in Pregnancy
- Universal screening and management of GBS bacteriuria in pregnancy are standards of care in the United States 5.
- Antibiotic prophylaxis is recommended for GBS positive patients with penicillin allergies, with cefazolin and vancomycin being the most frequently prescribed antibiotics 4.
- The American College of Obstetricians and Gynecologists (ACOG) guidelines recommend penicillin, ampicillin, or cefazolin for prophylaxis, with clindamycin and vancomycin reserved for cases of significant maternal penicillin allergy 3, 4.
Effectiveness of Antibiotic Prophylaxis
- Intrapartum antibiotic prophylaxis has been shown to be highly effective in preventing invasive GBS disease in the first week of life (early-onset) 6.
- The incidence of invasive early-onset GBS disease decreased by more than 80% from 1.8 cases/1000 live births in the early 1990s to 0.26 cases/1000 live births in 2010 6.