Key Facts

Group B Streptococcus (GBS, Streptococcus agalactiae) is a Gram-positive coccus that commonly colonises the gastrointestinal and genital tracts. It is the most frequent cause of early-onset neonatal sepsis, meningitis, and pneumonia in the UK.

Epidemiology

• Vaginal/rectal colonisation in 20-30% of pregnant women (transient, intermittent, or chronic)
• Early-onset GBS disease (EOGBS): 0.5 per 1,000 live births in the UK
• Late-onset GBS disease (7-90 days): 0.3 per 1,000 live births
• Vertical transmission rate: 50% of babies born to colonised mothers become colonised; 1-2% of these develop invasive disease

Aetiology

• Ascending infection from the maternal genital tract during labour
• Risk increases with prolonged rupture of membranes, preterm delivery, intrapartum fever
• Previous GBS disease in a sibling is the strongest risk factor

Pathophysiology

• GBS ascends through ruptured or intact membranes to the amniotic fluid
• Aspiration of infected amniotic fluid causes neonatal pneumonia
• Haematogenous spread leads to septicaemia and meningitis
• GBS capsular polysaccharide is the major virulence factor (serotype III most commonly causes meningitis)

Maternal Presentation

• Usually asymptomatic carrier
• May present with GBS urinary tract infection (bacteriuria)
• Rarely: chorioamnionitis, endometritis, wound infection

Neonatal Early-Onset Disease (<7 days, usually <24 hours)

• Respiratory distress (tachypnoea, grunting, nasal flaring)
• Temperature instability (hypothermia or fever)
• Poor feeding, lethargy
• Apnoea, cyanosis
• Signs of sepsis: tachycardia, poor perfusion, hypotension

Neonatal Late-Onset Disease (7-90 days)

• Meningitis (most common presentation)
• Fever, irritability, poor feeding
• Bulging fontanelle, seizures

Red Flags

• Respiratory distress within 6 hours of birth
• Temperature instability in first 24 hours
• Maternal fever in labour (>38°C)
• Prolonged ROM >18 hours with known GBS colonisation

Bedside

• Maternal observations (temperature, HR, BP)
• CTG if in labour
• Neonatal observations: HR, RR, temperature, SpO2

Bloods

• Maternal: midstream urine culture (GBS bacteriuria), vaginal/rectal swab if requested (not routine in UK)
• Neonatal: blood culture (before antibiotics), FBC, CRP
• Blood gas if respiratory distress

Imaging

• Neonatal CXR if respiratory distress
• Cranial USS if meningitis suspected

Special Tests

• Lumbar puncture: if neonatal meningitis suspected (CSF culture, protein, glucose)
• Surface swabs (ear, throat) of neonate for GBS
• Rapid antigen detection tests (limited sensitivity)

Non-pharmacological

• Awareness of risk factors and indications for IAP
• Patient information for GBS-positive women about signs of neonatal infection
• Neonatal observation: all babies born to GBS-positive mothers should have enhanced monitoring for ≥12 hours

Pharmacological

• Intrapartum antibiotic prophylaxis (IAP):
  • Benzylpenicillin: 3g IV loading dose, then 1.5g IV every 4 hours until delivery
  • Penicillin allergy (not anaphylaxis): cephalosporin (cefuroxime 1.5g IV 8-hourly)
  • Severe penicillin allergy: clindamycin 900mg IV 8-hourly (if GBS sensitive) or vancomycin 1g IV 12-hourly
• IAP should ideally be given ≥4 hours before delivery for maximum effectiveness
• Neonatal treatment: benzylpenicillin + gentamicin IV for suspected/confirmed EOGBS disease

Surgical/Interventional

• No specific surgical management
• Delivery should not be delayed to complete a course of IAP

Referral Criteria

• All neonates with suspected GBS infection require paediatric assessment
• Neonatal unit admission if symptomatic
• Follow-up hearing assessment for neonates with GBS meningitis

• EOGBS disease mortality: 5-10% overall; higher in preterm infants (up to 20%)
• EOGBS meningitis mortality: 10%; 25-50% of survivors have long-term neurological sequelae
• Late-onset GBS meningitis mortality: 2-6%
• IAP reduces EOGBS disease by approximately 86% (NNT approximately 200 for colonised women)
• With appropriate IAP, risk of neonatal disease is <0.5%

Indications for Intrapartum Antibiotic Prophylaxis (RCOG GTG 36)

UK vs USA Screening Approach