What is the treatment for a pregnant or reproductive-aged woman with Streptococcus agalactiae (Group B Streptococcus, GBS) vaginal discharge?

Treatment of Streptococcus agalactiae (Group B Streptococcus) Vaginal Discharge

Asymptomatic GBS vaginal colonization should NOT be treated with antibiotics outside of labor—treatment is reserved exclusively for intrapartum prophylaxis during active labor or for symptomatic urinary tract infections. 1, 2

Critical Context: When Treatment IS and IS NOT Indicated

Do NOT Treat Asymptomatic Vaginal Colonization

• Oral or intravenous antibiotics administered before labor are completely ineffective at eliminating GBS colonization and should never be used for asymptomatic vaginal discharge. 1, 2
• Prenatal antibiotic treatment fails because more than 30-70% of treated women remain colonized at delivery, and recolonization occurs rapidly even when sexual partners are treated. 1
• Treating asymptomatic colonization promotes antibiotic resistance, causes unnecessary adverse drug effects, and provides no clinical benefit. 1, 2

When Treatment IS Indicated

GBS bacteriuria (urinary tract infection):

• Any concentration of GBS in urine during pregnancy requires immediate treatment according to standard UTI protocols, followed by mandatory intrapartum prophylaxis during labor regardless of whether the UTI was treated. 2, 3
• GBS bacteriuria indicates heavy genital tract colonization and significantly increases the risk of early-onset neonatal disease. 2, 3

Intrapartum prophylaxis during active labor:

• All pregnant women with documented GBS colonization on vaginal-rectal screening cultures at 35-37 weeks gestation must receive IV antibiotics during active labor. 1, 2
• Women with GBS bacteriuria at any point during pregnancy automatically qualify for intrapartum prophylaxis without need for repeat screening. 1, 2

Screening Recommendations

• Universal vaginal-rectal screening should be performed at 36 0/7 to 37 6/7 weeks gestation using a single swab or two separate swabs. 1, 2
• Swab the lower vagina first, then insert the same swab through the anal sphincter into the rectum to maximize GBS detection. 2
• Women with GBS bacteriuria during pregnancy should not be re-screened, as they are presumed heavily colonized. 2

Intrapartum Antibiotic Prophylaxis Regimens

For Women Without Penicillin Allergy (First-Line)

• Penicillin G: 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery 1, 2
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery 1, 2
• Penicillin G is preferred due to its narrower spectrum and reduced selection pressure for resistant organisms. 1, 2

For Women With Penicillin Allergy (Not High-Risk for Anaphylaxis)

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery 1, 2
• Approximately 10% of penicillin-allergic patients also react to cephalosporins, so this is only for non-high-risk allergies. 1

For Women at High Risk for Anaphylaxis

• If GBS isolate is susceptible to clindamycin: Clindamycin 900 mg IV every 8 hours until delivery 1, 2
• If GBS isolate is resistant to clindamycin or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery 1, 2
• Susceptibility testing for clindamycin and erythromycin must be performed on prenatal GBS isolates from penicillin-allergic women at high risk for anaphylaxis. 1, 2
• Clindamycin resistance ranges from 3-15% and erythromycin resistance is 7-21% among GBS isolates, making susceptibility testing essential. 2, 4

Timing and Efficacy

• Intrapartum prophylaxis must be administered ≥4 hours before delivery for maximum effectiveness. 1, 2
• When given ≥4 hours before delivery, prophylaxis is 78-89% effective in preventing early-onset neonatal GBS disease. 1, 2
• Shorter durations (≥2 hours) may confer some protection, but efficacy is reduced. 1

Evaluation of Abnormal Vaginal Discharge

If a patient presents with abnormal vaginal discharge and GBS is identified:

• Evaluate for other treatable causes of discharge, including bacterial vaginosis (Gardnerella, Mobiluncus), candidiasis, and trichomoniasis. 2
• Treat these conditions according to standard protocols, but do not treat asymptomatic GBS colonization. 2
• Document GBS colonization for intrapartum prophylaxis planning during labor. 1, 2

Special Pregnancy Scenarios

Preterm labor (<37 weeks):

• Women admitted with signs of preterm labor who are GBS-positive or have unknown GBS status should receive GBS prophylaxis immediately at hospital admission. 2

Preterm premature rupture of membranes (PPROM):

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours is adequate for both latency prolongation and GBS prophylaxis. 2

Planned cesarean delivery:

• Women undergoing planned cesarean delivery before labor onset or membrane rupture should not routinely receive intrapartum GBS prophylaxis. 1

Critical Pitfalls to Avoid

• Never prescribe oral or IV antibiotics for asymptomatic GBS vaginal colonization during pregnancy—this is the most common and dangerous error. 1, 2
• Do not assume that treating GBS bacteriuria eliminates the need for intrapartum prophylaxis—recolonization is typical and intrapartum prophylaxis remains mandatory. 2
• Ensure adequate duration of prophylaxis (≥4 hours before delivery) for maximum effectiveness. 1, 2
• For penicillin-allergic patients at high risk for anaphylaxis, always obtain susceptibility testing before selecting clindamycin. 1, 2