What is the management approach for a pregnant woman with a vaginal swab showing gram-positive cocci in pairs, suggestive of Group B Streptococcus (GBS) colonization?

Management of Gram-Positive Cocci in Chains During Pregnancy

All pregnant women with vaginal gram-positive cocci in chains (presumptive Group B Streptococcus) detected on screening at 36-37 weeks gestation must receive intravenous antibiotic prophylaxis during active labor, not before. 1, 2

Critical Context: When Treatment IS and IS NOT Indicated

Do NOT treat asymptomatic GBS vaginal colonization with oral or IV antibiotics before labor. This approach is completely ineffective at eliminating colonization, promotes antibiotic resistance, and provides no benefit to mother or baby. 1, 2

Treatment IS Required For:

• GBS bacteriuria at any concentration during pregnancy - treat the UTI immediately AND provide intrapartum prophylaxis during labor 1, 2
• Previous infant with invasive GBS disease - automatic intrapartum prophylaxis, no screening needed 1
• Positive GBS screening culture at 36-37 weeks - intrapartum prophylaxis during active labor only 1, 2

Treatment IS NOT Required For:

• Asymptomatic vaginal colonization detected before labor - oral antibiotics are ineffective and harmful 1, 2
• Planned cesarean delivery before labor/membrane rupture - no prophylaxis needed regardless of GBS status 1

Screening Protocol

Screen all pregnant women at 36 0/7 to 37 6/7 weeks gestation using combined vaginal-rectal swab. 1, 2, 3

Proper Collection Technique:

• Swab lower vagina (2 cm into vaginal introitus) first, then insert same swab through anal sphincter into rectum (1 cm) 1, 4
• Do NOT use speculum - decreases GBS recovery 1
• Patient self-collection is acceptable with proper instruction 1, 4
• Place swab in transport medium (Amies or Stuart's) if laboratory is offsite 1

Laboratory Processing:

• Specimens require 1-4 hour incubation at 35-37°C in selective enrichment broth (SBM or Lim broth) 1
• Subculture onto blood agar after overnight incubation 1
• Report GBS in urine at ≥10,000 CFU/mL (≥10⁴ CFU/mL) 1, 2

Intrapartum Antibiotic Prophylaxis Regimens

For Women WITHOUT Penicillin Allergy:

Penicillin G is the preferred agent due to narrow spectrum and universal GBS susceptibility. 1, 2

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery 1, 2
• Ampicillin (alternative): 2 g IV initially, then 1 g IV every 4 hours until delivery 1

For Women WITH Penicillin Allergy:

Risk stratification is essential. High-risk allergy includes history of anaphylaxis, angioedema, respiratory distress, or urticaria after penicillin or cephalosporin. 1, 2

NOT High-Risk for Anaphylaxis:

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery 1, 2

High-Risk for Anaphylaxis:

Susceptibility testing MUST be performed on prenatal GBS isolates. 1, 2

• If susceptible to clindamycin: Clindamycin 900 mg IV every 8 hours until delivery 1, 2
• If resistant or unknown susceptibility: Vancomycin 1 g IV every 12 hours until delivery 1, 2
• Test for inducible clindamycin resistance if isolate is clindamycin-susceptible but erythromycin-resistant 1, 2

Timing and Efficacy

Administer prophylaxis ≥4 hours before delivery for maximum effectiveness. When given ≥4 hours before delivery, intrapartum prophylaxis reduces early-onset neonatal GBS disease by 78%. 2, 3

If GBS Status Unknown at Labor Onset:

Provide intrapartum prophylaxis if ANY of the following risk factors present: 1

• Gestational age <37 weeks
• Membrane rupture ≥18 hours
• Intrapartum temperature ≥100.4°F (≥38.0°C)

Special Clinical Scenarios

GBS Bacteriuria During Pregnancy:

Any concentration of GBS in urine requires immediate treatment AND intrapartum prophylaxis during labor, regardless of whether UTI was treated earlier. 1, 2 GBS bacteriuria indicates heavy genital tract colonization and increases neonatal disease risk 29-fold. 2, 4

Preterm Premature Rupture of Membranes (PPROM):

For PPROM ≥24 weeks with unknown GBS status: Start ampicillin 2 g IV once, then 1 g IV every 6 hours for at least 48 hours - this regimen provides both latency prolongation and adequate GBS prophylaxis. 5

Previous GBS-Positive Pregnancy:

If GBS status unknown in current pregnancy and patient presents in labor: Provide intrapartum prophylaxis based on history alone. 4

Common Pitfalls to Avoid

• Never treat asymptomatic vaginal GBS colonization with oral antibiotics before labor - this is ineffective and promotes resistance 1, 2
• Do not assume treating GBS UTI eliminates need for intrapartum prophylaxis - recolonization is typical, intrapartum IV prophylaxis remains mandatory 2
• Do not collect cervical cultures or use speculum - decreases GBS recovery 1
• Do not screen before 36 weeks or after 37 6/7 weeks - results become unreliable outside this window 1, 3
• Do not give prophylaxis for planned cesarean delivery before labor/membrane rupture - unnecessary regardless of GBS status 1

Documentation Requirements

Ensure laboratory results are communicated to both the anticipated delivery site and ordering provider, with 24/7 access to culture results. 1