What about Group B streptococcal disease prevention?

Group B Streptococcal Disease Prevention

All pregnant women should undergo universal screening for GBS colonization at 36 0/7 to 37 6/7 weeks' gestation using combined vaginal-rectal swabs, with intrapartum antibiotic prophylaxis administered to all carriers during labor. 1, 2

Screening Strategy

Universal prenatal screening is the recommended approach rather than risk-based strategies alone. 3, 1

• Perform vaginal-rectal culture screening at 36 0/7 to 37 6/7 weeks' gestation using a single swab inserted first into the vagina, then through the anal sphincter into the rectum. 1, 4, 2
• Screen all women, including those planning cesarean delivery, due to risk of labor or membrane rupture before scheduled surgery. 4
• Nucleic acid amplification tests may be considered as an alternative to routine culture for enhanced sensitivity. 5

Indications for Intrapartum Antibiotic Prophylaxis

Administer IV antibiotics during labor to women with:

• Positive GBS screening culture at 36-37 weeks' gestation 1, 2
• GBS bacteriuria at any level during current pregnancy (≥10⁴ CFU/mL) - these women require treatment at diagnosis AND intrapartum prophylaxis, and do NOT need repeat screening at 36-37 weeks 1, 6, 4, 5
• Previous infant with invasive GBS disease 4
• Unknown GBS status at term (≥37 weeks) with membrane rupture >18 hours 4
• Any woman <37 weeks' gestation in labor or with ruptured membranes (unless negative culture/test within prior 5 weeks) 4

Antibiotic Regimens

First-line agents:

• Penicillin G (preferred): 5 million units IV initial dose, then 2.5-3 million units IV every 4 hours until delivery 1, 5
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery 1
• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours until delivery (for women with minor penicillin allergy) 5, 2

For women with significant penicillin allergy risk (anaphylaxis):

• Obtain antibiotic susceptibility testing on GBS isolates 4, 5
• Clindamycin 900 mg IV every 8 hours if organism is susceptible 5, 2
• Vancomycin 1 g IV every 12 hours if clindamycin resistance or susceptibility unknown 5, 2
• Consider penicillin allergy skin testing to confirm true allergy status, as this provides both immediate and long-term health benefits 7

Special Clinical Scenarios

Pre-labor rupture of membranes at term (≥37 weeks):

• If GBS-positive: immediate induction of labor with concurrent IV antibiotic prophylaxis - expectant management is not supported by evidence for safe neonatal outcomes 4

Pre-labor rupture of membranes preterm (<37 weeks):

• Administer IV GBS prophylaxis for 48 hours while awaiting spontaneous or indicated labor, plus additional antibiotics if clinically indicated 4

Intrapartum fever with chorioamnionitis:

• Treat with broad-spectrum IV antibiotics that include GBS coverage, regardless of GBS status or gestational age 4

Timing and Effectiveness

• Optimal prophylaxis requires ≥4 hours of antibiotic administration before delivery for maximum effectiveness 2
• Even 2 hours of antibiotic exposure reduces GBS vaginal colony counts and decreases clinical neonatal sepsis, though less effective than ≥4 hours 2
• Do not delay necessary obstetric interventions solely to achieve 4 hours of antibiotic administration 2

Critical Distinctions for Non-Pregnant Populations

GBS bacteriuria in non-pregnant adults should NOT be treated if asymptomatic - treatment is only indicated for symptomatic UTI or underlying urinary tract abnormalities. 1, 6

Clinical Impact

• GBS remains the leading cause of early-onset neonatal sepsis in the United States, with case-fatality rates of 5-20% for newborns 3
• Survivors may suffer permanent disabilities including hearing loss, visual impairment, or intellectual disability 3
• Intrapartum antibiotic prophylaxis has proven highly effective in preventing early-onset disease, though no current strategy prevents late-onset GBS disease 7