What are the guidelines for preventing and treating Group B Streptococcus (GBS) infection, also known as strep agalactiae, in pregnant women and newborns?

Prevention and Treatment of Group B Streptococcus (GBS) in Pregnancy and Newborns

All pregnant women should be screened at 35-37 weeks' gestation for vaginal and rectal GBS colonization, and intrapartum antibiotic prophylaxis should be given to all women identified as GBS carriers to prevent early-onset GBS disease. 1

Universal Screening and Indications for Prophylaxis

• Pregnant women should undergo universal screening for GBS colonization between 35-37 weeks' gestation with both vaginal and rectal specimens 1
• Women with GBS isolated from urine at any concentration during the current pregnancy should receive intrapartum antibiotic prophylaxis without need for additional screening 1, 2
• Women who previously gave birth to an infant with invasive GBS disease should receive intrapartum prophylaxis without additional screening 1
• If GBS status is unknown at labor onset, intrapartum prophylaxis should be administered to women with any of these risk factors: gestation <37 weeks, membrane rupture ≥18 hours, or temperature ≥100.4°F (≥38.0°C) 1

Specimen Collection and Processing

• Collection should involve swabbing the lower vagina and rectum (through the anal sphincter) 1
• Specimens can be collected by either the patient with appropriate instruction or healthcare provider 1, 3
• Specimens should be placed in nonnutritive transport medium and clearly labeled for GBS culture 1
• Laboratories should use techniques that maximize GBS recovery, including 1-4 hour incubation in appropriate enrichment broth medium 1

Antibiotic Prophylaxis Regimens

• For women without penicillin allergy: Penicillin G, 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery 1
• Alternative for non-allergic women: Ampicillin, 2g IV initial dose, then 1g IV every 4 hours until delivery 1
• For penicillin-allergic women, susceptibility testing should guide alternative therapy 2
• Antimicrobial agents should not be used before the intrapartum period to eradicate GBS colonization, as this is ineffective and may cause adverse consequences 1, 4

Special Situations

Preterm Labor Management

• For women with threatened preterm labor: obtain vaginal-rectal swab for GBS culture and start GBS prophylaxis 1
• If determined not to be in true labor, discontinue GBS prophylaxis 1
• If GBS culture results become available and are negative, discontinue prophylaxis 1
• For women with preterm premature rupture of membranes (pPROM): obtain GBS culture and start antibiotics 1
• Antibiotics given for latency in pPROM that include ampicillin 2g IV once, followed by 1g IV every 6 hours for at least 48 hours are adequate for GBS prophylaxis 1

Cesarean Delivery

• Women with planned cesarean delivery before labor onset and with intact membranes are at low risk for early-onset GBS disease and do not require routine intrapartum prophylaxis, regardless of GBS colonization status 1, 4

GBS Urinary Tract Infection in Pregnancy

• All GBS isolates from urine should be treated regardless of colony count, as GBS bacteriuria is a marker for heavy genital tract colonization 4
• Women with symptomatic or asymptomatic GBS UTI during pregnancy should receive treatment according to standard UTI protocols 4
• These women must also receive intrapartum antibiotic prophylaxis during labor and do not need additional GBS screening at 35-37 weeks 4

Neonatal Considerations

• Separate consideration should be given to infants born at <35 weeks and ≥35 weeks gestation when performing GBS risk assessment 5
• Empiric antibiotics are recommended for infants at high risk for GBS early-onset disease 5
• Current prevention strategies are effective for early-onset disease but do not prevent late-onset GBS disease 5

Common Pitfalls and Caveats

• Attempting to eradicate GBS colonization before labor with antibiotics is ineffective and may cause adverse consequences 4
• Withholding intrapartum prophylaxis for women with history of GBS bacteriuria in the current pregnancy, even if subsequent cultures are negative, is not recommended 4
• GBS colonization during a previous pregnancy is not an indication for prophylaxis in subsequent deliveries without current positive screening 1
• Despite prevention efforts, GBS remains a leading cause of neonatal morbidity and mortality requiring continued vigilance 3
• Increasing antibiotic resistance, particularly to second-line antibiotics like erythromycin and clindamycin, is a growing concern 6