What is the treatment for Group B streptococcal (GBS) infection in the vagina?

Treatment for Group B Streptococcus (GBS) in the Vagina

If you are pregnant, vaginal GBS colonization should NOT be treated with antibiotics outside of active labor—oral antibiotics during pregnancy are ineffective at eliminating colonization and may cause harm through antibiotic resistance and adverse effects. 1, 2

Critical Context: Pregnancy vs. Non-Pregnancy

The management of vaginal GBS differs fundamentally based on pregnancy status:

If You Are Pregnant

Do NOT treat vaginal GBS colonization with oral antibiotics during pregnancy. 1, 2 This approach:

• Fails to eliminate carriage effectively 1
• Promotes antibiotic resistance 1, 2
• May cause adverse drug effects without benefit 1

The correct approach is:

• Screen for GBS at 36-37 weeks gestation with vaginal-rectal culture 1, 2
• Treat ONLY during active labor with intravenous antibiotics (intrapartum prophylaxis) 1, 2

Intrapartum antibiotic regimen (during labor):

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery (preferred agent due to narrow spectrum) 1, 2
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery 1, 2

For penicillin-allergic patients:

• Not at high risk for anaphylaxis: Cefazolin 2 g IV initially, then 1 g IV every 8 hours 1, 2
• High risk for anaphylaxis with susceptible isolate: Clindamycin 900 mg IV every 8 hours 1, 2
• High risk with resistant or unknown susceptibility: Vancomycin 1 g IV every 12 hours 1, 2

Special Pregnancy Situations Requiring Treatment

GBS bacteriuria (any concentration in urine) during pregnancy:

• Requires immediate treatment of the UTI 2, 3
• PLUS mandatory intrapartum prophylaxis during labor regardless of prior treatment 2
• This indicates heavy colonization and increased risk of neonatal disease 2

Preterm labor or preterm premature rupture of membranes:

• Start GBS prophylaxis immediately at admission if GBS status unknown or positive 2, 4
• For PPROM ≥24 weeks: Ampicillin 2 g IV once, then 1 g IV every 6 hours for at least 48 hours provides both latency and GBS coverage 2, 4

If You Are NOT Pregnant

Asymptomatic vaginal GBS colonization requires no treatment. 3 GBS is normal vaginal flora in 10-40% of women and does not cause disease in non-pregnant adults unless there is a symptomatic urinary tract infection. 5, 6

Treatment is only indicated if:

• You have symptomatic UTI with GBS in urine 3
• You have underlying urinary tract abnormalities 3

For symptomatic GBS UTI in non-pregnant patients:

• Penicillin 500 mg orally every 6-8 hours for 7-10 days (preferred) 3
• Alternative: Ampicillin 500 mg orally every 8 hours for 7-10 days 3
• Penicillin allergy: Clindamycin 300-450 mg orally every 8 hours (requires susceptibility testing) 3

Common Pitfalls to Avoid

Never treat asymptomatic vaginal GBS colonization during pregnancy with oral antibiotics. 1, 2 This is the most common error and provides no benefit while causing potential harm.

Do not confuse vaginal colonization with urinary tract infection. 2 GBS bacteriuria at any concentration during pregnancy requires both immediate treatment AND intrapartum prophylaxis, whereas vaginal colonization alone only requires intrapartum prophylaxis. 2

Planned cesarean delivery before labor/membrane rupture does not require GBS prophylaxis. 1 These women are at low risk for transmitting GBS to the infant.

A negative GBS screen is only valid for 5 weeks. 1 If delivery occurs more than 5 weeks after screening, repeat the culture. 1

Why This Approach Matters

Intrapartum antibiotic prophylaxis during labor reduces early-onset neonatal GBS infection from 4.7% to 0.4%. 7 This strategy has resulted in an 80% reduction in early-onset neonatal GBS disease in countries with systematic screening programs. 6 The key is timing—antibiotics must be given during labor to prevent transmission during delivery, not weeks earlier when they cannot eliminate colonization. 1, 2