Group B Streptococcus Infections
Disease Characteristics
- Group B Streptococcus infections in newborns typically develop within the first 24-48 hours of life for early-onset disease, while late-onset disease occurs between 7 days and 3 months of age 1
- Early-onset GBS disease is characterized by presentation primarily within the first 24-48 hours of life, with most cases manifesting with respiratory distress, apnea, or other signs of sepsis, and common clinical syndromes including sepsis and pneumonia; less frequently meningitis 1
- Late-onset disease presents more commonly as meningitis compared to early-onset disease 2
- Clinical manifestations of GBS infection can include sepsis, pneumonia, meningitis, osteomyelitis, septic arthritis, bacteremia, endometritis, and amnionitis 1, 3
Risk Factors
- Maternal GBS colonization is a primary risk factor, with colonized mothers being >25 times more likely to deliver infants with early-onset disease 1
- The following risk factors increase the likelihood of GBS infection:
- The following table summarizes the risk factors for GBS infection:
| Risk Factor | Description |
|---|---|
| Colonization | 10-30% of pregnant women are colonized with GBS |
| Prolonged rupture of membranes | Especially more than 18 hours |
| Preterm labor | Less than 37 weeks of gestation |
| Intrapartum fever | Greater than 38°C |
| GBS bacteriuria | Indicates heavy colonization |
| Previous child with invasive GBS disease | Increases risk for subsequent pregnancies |
| Young maternal age | Less than 20 years |
| Black race | Increases risk of GBS infection |
| Low maternal levels of anticapsular antibodies | Increases risk of GBS infection |
| Advanced age | Increases risk of GBS bacteremia |
| Diabetes mellitus | Primary predisposing factor in adults |
| Underlying medical conditions | Compromises immune system and increases risk of GBS bacteremia |
Transmission and Prevention
- Vertical transmission occurs when GBS ascends from the vagina to amniotic fluid after labor onset or membrane rupture, invades through intact membranes, or infants are exposed during passage through the birth canal 1
- Without intervention, approximately 1-2% of infants born to GBS-colonized mothers develop early-onset disease 1
- The American College of Obstetricians and Gynecologists and the Centers for Disease Control and Prevention recommend universal screening at 36-37 weeks gestation and appropriate intrapartum antibiotic prophylaxis to prevent early-onset GBS disease, although this does not prevent late-onset disease 1
- The CDC recommends intrapartum antibiotic prophylaxis for women with identified GBS colonization in prenatal cultures at 35-37 weeks, those with GBS bacteriuria during the current pregnancy, those with a history of a previous child with invasive GBS disease, and those with preterm labor or premature rupture of membranes 1, 2
- Penicillin G is the first-line antibiotic of choice, with ampicillin as an acceptable alternative 2
Mortality and Morbidity
- Mortality is significantly higher among preterm infants, with a 20% case-fatality rate overall, up to 30% for those ≤33 weeks' gestation, and 2-3% for full-term infants 1
- The mortality rate for GBS disease is estimated to be 5-20% for newborns and 15-32% for adults 3
- The case-fatality ratio has declined from as high as 50% in the 1970s to 4-6% in recent years due to advances in neonatal care 1