What is the recommended treatment for a positive Group A strep (Streptococcus pyogenes) test in the perinatal setting?

Group A Streptococcus in the Perinatal Setting

Critical Clarification: Group A vs. Group B Streptococcus

The evidence provided addresses Group B Streptococcus (GBS), not Group A Streptococcus (GAS), which are entirely different pathogens requiring distinct management approaches. Group B Streptococcus is the leading cause of neonatal early-onset sepsis and is the focus of universal prenatal screening and intrapartum prophylaxis protocols 1. Group A Streptococcus (Streptococcus pyogenes) is a different organism that causes invasive infections in postpartum mothers and occasionally neonates, but is not part of routine prenatal screening 2.

Management for Group A Streptococcus (GAS) in Perinatal Setting

Maternal iGAS Infection

If a mother develops invasive Group A Streptococcal infection within 28 days postpartum, both mother and neonate should receive antibiotic treatment immediately. The incidence of iGAS in postpartum women is dramatically elevated at 109 per 100,000 person-years compared to 1.3 per 100,000 in non-pregnant women aged 15-44 2.

• Median onset for maternal iGAS is 2 days postpartum (IQR 0-5 days) 2
• All eligible neonates (89%) should receive chemoprophylaxis when maternal iGAS is identified 2
• Penicillin G is the first-line treatment for GAS infections, with doses of 12-20 million units/day divided every 4-6 hours 3, 4
• For penicillin-allergic patients with high anaphylaxis risk, use clindamycin (if susceptible) or vancomycin 3, 5

Neonatal iGAS Infection

If a neonate develops iGAS within 28 days of birth, treat both the infant and mother with antibiotics. Neonatal iGAS has an incidence of 1.5 per 100,000 person-years with median onset at 12 days (IQR 7-15 days) 2.

• Empirical therapy for neonatal sepsis should be ampicillin plus gentamicin 1
• Ampicillin dosing for neonates: 100-200 mg/kg/day divided in 4-6 doses 3
• Gentamicin dosing: 3 mg/kg/day 3

Cluster Investigation

• Save GAS isolates from all maternity cases for molecular comparison to identify potential transmission 2
• Investigate clusters when multiple cases occur in the same maternity unit within 6 months 2
• Only 2 of 20 clusters showed possible transmission, but isolate storage was inadequate in 6 of 15 clusters even after guidance was issued 2

Management for Group B Streptococcus (GBS) - The More Common Perinatal Pathogen

Maternal Screening and Intrapartum Prophylaxis

Universal GBS screening should occur at 36 0/7 to 37 6/7 weeks of gestation (updated from 35-37 weeks) 6, 7. This represents the most recent guideline change.

Indications for intrapartum antibiotic prophylaxis (IAP) include: 1

• GBS-positive culture within preceding 5 weeks
• GBS bacteriuria during current pregnancy
• History of previous infant with GBS disease
• Unknown GBS status with risk factors: <37 weeks gestation, membrane rupture ≥18 hours, or temperature ≥100.4°F (38.0°C)

Adequate IAP is defined as ≥4 hours of penicillin (preferred), ampicillin, or cefazolin before delivery 1, 3.

• Penicillin G: 5 million units IV initially, then 2.5-3 million units every 4 hours until delivery 3
• Ampicillin: 2g IV initially, then 1g every 4 hours until delivery 3
• Cefazolin is preferred for penicillin-allergic patients at low risk for anaphylaxis 1

Penicillin Allergy Management

Approximately 20% of GBS isolates are resistant to clindamycin, so susceptibility testing must always be performed before using clindamycin for IAP 1, 3.

• For high-risk anaphylaxis patients, use vancomycin if susceptibility results are unavailable 1, 3
• Clindamycin should never be used without documented susceptibility testing 1
• Pregnant women with penicillin allergy history should undergo skin testing for potential delabeling 6

Neonatal Management Algorithm

All newborns with signs of sepsis require full diagnostic evaluation (including lumbar puncture if stable) and empirical IV ampicillin plus gentamicin immediately 1.

• 15-38% of infants with early-onset meningitis have sterile blood cultures, making lumbar puncture essential 1

Well-appearing infants born to mothers with chorioamnionitis require limited evaluation (CBC, blood culture) and empirical antibiotics 1.

• CBC sensitivity improves if delayed 6-12 hours after birth 1
• Discontinue empirical therapy once sepsis is excluded 1

Well-appearing term infants whose mothers received adequate IAP require only observation for ≥48 hours 1.

• May discharge at 24 hours if term, ready access to care exists, and reliable caregiver present 1
• Follow-up within 48-72 hours mandatory 1

Well-appearing term infants with inadequate/no IAP and membrane rupture <18 hours require observation for 48 hours only 1.

Well-appearing term infants with inadequate/no IAP and membrane rupture ≥18 hours require limited evaluation and observation for ≥48 hours 1.

All preterm infants (<37 weeks) with inadequate/no IAP require limited evaluation and observation for ≥48 hours 1.

Common Pitfalls

• Clindamycin and vancomycin are considered inadequate IAP regardless of duration due to lack of efficacy data and unfavorable pharmacokinetics 1
• IAP duration <4 hours is inadequate, though 2 hours reduces vaginal colony counts and may decrease clinical sepsis 7, 8
• Do not delay necessary obstetric interventions solely to achieve 4 hours of antibiotic administration 7
• Cesarean delivery before labor onset with intact membranes does not require IAP regardless of GBS status 1