When to treat Group B Streptococcus (GBS) in the vagina?

From the Guidelines

Vaginal strep B typically doesn't require treatment unless specific circumstances exist, such as a positive screening culture at 35-37 weeks gestation during pregnancy, with intravenous antibiotics administered during labor to prevent transmission to the newborn 1. When considering treatment for vaginal strep B, it's essential to prioritize the prevention of early-onset group B streptococcal disease in newborns.

• The Centers for Disease Control and Prevention (CDC) recommends routine screening for GBS colonization at 35-37 weeks gestation in all pregnant women 1.
• Intrapartum antibiotic prophylaxis is indicated for women with a positive GBS vaginal-rectal screening culture in late gestation, previous infant with invasive GBS disease, or GBS bacteriuria during any trimester of the current pregnancy 1.
• The recommended regimen for intrapartum chemoprophylaxis is penicillin G, 5 million units intravenously initial dose, then 2.5 million units intravenously every 4 hours until delivery, or ampicillin, 2 g intravenously initial dose, then 1 g intravenously every 4 hours until delivery 1.
• For penicillin-allergic women, alternative regimens include cefazolin, clindamycin, or erythromycin, depending on the severity of the allergy and the susceptibility of the GBS isolate 1.
• Outside of pregnancy, vaginal GBS is generally considered part of normal flora and doesn't require treatment unless it's causing symptomatic infection or in patients with specific risk factors.
• Treatment decisions should be based on clinical symptoms and risk factors rather than just the presence of the bacteria, as asymptomatic colonization is common and typically benign in non-pregnant women.

From the Research

Treatment of Vaginal Strep B

• The Centers for Disease Control and Prevention (CDC) recommends universal vaginal-rectal screening for Group B Streptococcus (GBS) colonization in pregnant women between 35 and 37 weeks of gestation, aimed at intrapartum antibiotic prophylaxis (IAP) 2.
• IAP is the only currently available and highly effective method against early onset GBS neonatal infections 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 3.
• Intrapartum antibiotic prophylaxis in women who carry GBS, from the onset of labor until delivery, reduces the risk of early-onset neonatal GBS infection from 4.7% to 0.4% (p = 0.02) 3.
• Penicillin G (benzylpenicillin) is the antibiotic of choice, while penicillin A (ampicillin or amoxicillin) is an alternative 3.
• In case of penicillin allergy, erythromycin or clindamycin are generally active against GBS and carry no particular risks for the infant 3.
• The American College of Obstetricians and Gynecologists (ACOG) recommends that women with a history of penicillin allergy should be evaluated for the severity of their allergy and alternative antibiotics should be used if necessary 4.
• Alternative antibiotic use for GBS prophylaxis is frequent with penicillin/cephalosporin allergies, and efforts to confirm allergy and perform penicillin hypersensitivity testing may increase compliance with guidelines for antibiotic administration 4.
• At least 4 hours of intrapartum antibiotic prophylaxis is recommended to prevent early-onset GBS disease 5.

Timing of Treatment

• The CDC recommends that IAP should be administered at least 4 hours before delivery to maximize its effectiveness 2, 5.
• However, even 2 hours of antibiotic prophylaxis shows some pharmacological benefit, but 4 hours is the most effective method of preventing early-onset GBS disease 5.
• Obstetricians should consider strengthening the beneficial effect of intrapartum antibiotic prophylaxis for infants exposed to GBS by providing at least 4 hours of treatment coverage 5.