What is the management approach for a pregnant woman with a vaginal swab showing gram-positive cocci in pairs, suggestive of Group B Streptococcus (GBS) colonization?

Management of Vaginal Gram-Positive Cocci in Pairs (GBS) in Pregnancy

If you are pregnant, do NOT treat the vaginal colonization now—only provide intravenous antibiotics during active labor to prevent neonatal disease. 1, 2

Critical Context: When GBS Treatment IS and IS NOT Indicated

Do NOT Treat Before Labor

• Oral or IV antibiotics given before labor are completely ineffective at eliminating GBS colonization and should never be used for asymptomatic vaginal colonization. 3, 1
• Prenatal treatment outside the intrapartum period promotes antibiotic resistance, causes unnecessary adverse drug effects, and provides zero clinical benefit for preventing neonatal disease. 1, 2
• Even if you treat GBS colonization weeks before delivery, recolonization occurs rapidly, making the treatment futile. 1

DO Treat During Labor (Intrapartum Prophylaxis)

• All pregnant women with documented GBS colonization on vaginal-rectal culture at 35-37 weeks (updated to 36 0/7-37 6/7 weeks) must receive IV antibiotics during active labor. 3, 2
• Intrapartum antibiotic prophylaxis administered ≥4 hours before delivery reduces early-onset neonatal GBS disease by 78%. 1, 2
• This approach has reduced early-onset GBS disease incidence by 70% and prevents approximately 4,500 cases and 225 deaths annually in the United States. 2

Immediate Actions Based on Clinical Scenario

If Patient is Currently Pregnant

Step 1: Determine if this is colonization or infection

• If the patient has a symptomatic urinary tract infection with GBS (dysuria, frequency, urgency, fever), treat the acute UTI immediately with pregnancy-safe antibiotics. 1, 4
• If GBS bacteriuria is present at ANY concentration (even <10,000 CFU/mL), this indicates heavy genital colonization and mandates both immediate UTI treatment AND intrapartum prophylaxis during labor. 1, 2
• If this is asymptomatic vaginal colonization only (no UTI symptoms), do NOT prescribe antibiotics now. 3, 1

Step 2: Document and communicate

• Ensure the GBS-positive status is clearly documented in the prenatal record and communicated to the anticipated delivery site. 3
• The patient should be informed that she will receive IV antibiotics during labor, not oral antibiotics now. 3

Step 3: Plan for intrapartum prophylaxis

• First-line regimen: Penicillin G 5 million units IV initially, then 2.5-3 million units IV every 4 hours until delivery. 1, 2
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery (broader spectrum, less preferred). 1

For Penicillin-Allergic Patients

Risk stratification is essential:

• Low-risk allergy (rash only, no anaphylaxis history): Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery. 1, 2
• High-risk allergy (history of anaphylaxis, angioedema, urticaria, or asthma): Clindamycin 900 mg IV every 8 hours IF the GBS isolate is susceptible. 1, 2
• If clindamycin resistance or unknown susceptibility: Vancomycin 1 g IV every 12 hours until delivery. 1, 2
• Susceptibility testing for clindamycin and erythromycin MUST be performed on GBS isolates from high-risk penicillin-allergic patients. 1, 2

Special Clinical Scenarios

GBS Bacteriuria During Pregnancy

• Any concentration of GBS in urine during pregnancy requires immediate treatment of the UTI AND mandatory intrapartum prophylaxis during labor, regardless of whether the UTI was treated earlier. 1, 2
• GBS bacteriuria is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal disease. 1
• Women with GBS bacteriuria do NOT need repeat vaginal-rectal screening at 35-37 weeks—they are presumed colonized and automatically qualify for intrapartum prophylaxis. 1

Preterm Labor or PPROM

• Women admitted with signs of preterm labor (<37 weeks) with unknown GBS status or positive GBS screen within 5 weeks should receive GBS prophylaxis immediately at hospital admission. 1
• For preterm premature rupture of membranes (PPROM) at ≥24 weeks, ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours is adequate for both latency prolongation and GBS prophylaxis. 1

Planned Cesarean Delivery

• Women undergoing planned cesarean delivery before labor onset and before membrane rupture do NOT routinely require intrapartum GBS prophylaxis. 3, 1

Screening Recommendations

Optimal Screening Technique

• Collect vaginal-rectal swabs at 36 0/7-37 6/7 weeks gestation using a single swab or two separate swabs. 3, 2
• Swab the lower vagina (vaginal introitus) first, then insert the same swab through the anal sphincter into the rectum. 3
• Do NOT use a speculum—this reduces GBS detection by 5-27%. 3
• Place swabs in non-nutritive transport medium (Amies or Stuart's media without charcoal). 3, 2

Laboratory Processing

• The laboratory must use selective broth medium (SBM or Lim broth) with overnight incubation, then subculture onto blood agar. 3, 2
• Selective media increase GBS detection by up to 50% compared to direct plating. 3
• Laboratories should report results to both the anticipated delivery site and the ordering provider, with 24/7 access to results. 3

Common Pitfalls to Avoid

• Never prescribe oral antibiotics (amoxicillin, cephalexin, etc.) for asymptomatic GBS vaginal colonization during pregnancy—this is ineffective and harmful. 3, 1
• Do not assume that treating a GBS UTI in the second trimester eliminates the need for intrapartum prophylaxis—recolonization is typical. 1
• Do not rely on vaginal cultures alone—adding rectal swabs increases detection by 5-27%. 3
• Do not use cervical cultures—these are not recommended and miss many colonized women. 3
• Approximately 10% of patients with penicillin allergy also have immediate hypersensitivity to cephalosporins, making allergy risk stratification critical. 1
• Clindamycin resistance ranges from 3-15% in GBS isolates, making susceptibility testing essential for high-risk allergic patients. 1

Risk Factors for Early-Onset Neonatal GBS Disease

• Maternal GBS colonization increases neonatal disease risk 29-fold compared to non-colonized mothers. 3
• Prematurity (<37 weeks), prolonged membrane rupture (≥18 hours), and intrapartum fever (≥100.4°F/38°C) each increase risk approximately 7-fold. 3
• Maternal age <20 years and Black race are associated with higher incidence. 3
• Previous delivery of an infant with GBS disease mandates intrapartum prophylaxis in all subsequent pregnancies without need for screening. 3, 2

Neonatal Outcomes Without Prophylaxis

• Approximately 1-2% of infants born to colonized mothers develop early-onset invasive disease without intrapartum prophylaxis. 3
• Early-onset GBS disease accounts for 80% of neonatal GBS infections, with case-fatality rates of 5-20%. 3
• Long-term neurologic sequelae occur in 15-30% of meningitis survivors. 3
• The gastrointestinal tract is the primary human reservoir, with secondary spread to the genitourinary tract. 3