Management of Group B Streptococcus Bacteriuria
Critical First Principle: Pregnancy Status Determines Everything
In pregnant women, any concentration of GBS in urine—regardless of symptoms or colony count—mandates immediate treatment of the urinary infection and obligatory intravenous intrapartum antibiotic prophylaxis during labor. 1, 2 In contrast, asymptomatic GBS bacteriuria in non-pregnant adults should not be treated except before urologic procedures involving mucosal trauma. 1
Management in Pregnant Women
Immediate Actions Required
Treat the acute UTI at diagnosis using standard pregnancy-safe antibiotics if the patient is symptomatic, but understand that this treatment does NOT eliminate GBS colonization from the genitourinary tract. 1, 2
Document the finding prominently in the prenatal record and communicate to the anticipated delivery site, because this patient automatically qualifies for intrapartum prophylaxis regardless of when the bacteriuria occurred or whether it was treated. 1
Do NOT re-screen this patient with vaginal-rectal cultures at 36–37 weeks gestation—she is presumed heavily colonized and requires intrapartum prophylaxis. 1, 3
Why GBS Bacteriuria Is Clinically Significant in Pregnancy
GBS bacteriuria at any concentration is a marker for heavy genital tract colonization and increases the risk of early-onset neonatal GBS disease more than 25-fold compared to non-colonized mothers. 1, 4
Even low colony counts (<10⁴ CFU/mL) are associated with elevated risk for neonatal disease and intrapartum colonization. 1, 5
Mandatory Intrapartum Prophylaxis Protocol
Timing: Administer IV antibiotics during active labor, continuing until delivery; optimal effectiveness requires ≥4 hours of antibiotic exposure before birth, which reduces early-onset neonatal disease by 78–89%. 1
First-line regimen (no penicillin allergy):
Penicillin G: 5 million units IV loading dose, then 2.5–3.0 million units IV every 4 hours until delivery (preferred agent due to narrow spectrum and universal GBS susceptibility). 1
Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative). 1
Penicillin-allergic patients—low-risk allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):
- Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery. 1
Penicillin-allergic patients—high-risk allergy (history of anaphylaxis or severe immediate reactions):
Obtain clindamycin and erythromycin susceptibility testing immediately on the GBS isolate, because clindamycin resistance ranges from 3–15% and erythromycin resistance from 7–21%. 1, 6
If susceptible to both agents: Clindamycin 900 mg IV every 8 hours until delivery. 1
If resistant to either agent or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery. 1
If susceptible to clindamycin but resistant to erythromycin: Perform D-zone testing to detect inducible clindamycin resistance; use clindamycin only if D-zone test is negative. 1
Special Pregnancy Scenarios
Preterm labor (<37 weeks) with GBS bacteriuria:
- Start GBS prophylaxis immediately upon hospital admission; discontinue if preterm labor is ruled out. 1
Preterm premature rupture of membranes (PPROM):
- Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours provides both latency prolongation and adequate GBS prophylaxis. 1
Critical Pitfall to Avoid
Never assume that treating the UTI with oral antibiotics during pregnancy eliminates the need for intrapartum IV prophylaxis. 1, 2 Recolonization after oral antibiotics is typical, and only IV antibiotics administered ≥4 hours before delivery are effective in preventing neonatal disease. 1
Management in Non-Pregnant Adults
When NOT to Treat (Most Common Scenario)
Do NOT treat asymptomatic GBS bacteriuria in non-pregnant adults, regardless of colony count. 1 This includes:
- Elderly or institutionalized individuals 1
- Patients with diabetes mellitus 1
- Patients with indwelling urinary catheters (short- or long-term) 1
- Patients with neurogenic bladder on intermittent catheterization 1
- Patients undergoing non-urologic surgery (including orthopedic procedures) 1
- Patients with recurrent UTI history 1
Rationale: Treating asymptomatic bacteriuria leads to unnecessary antibiotic exposure, promotes antimicrobial resistance, increases risk of Clostridioides difficile infection, and provides no clinical benefit. 1
When TO Treat
Treat GBS bacteriuria in non-pregnant adults ONLY when:
Classic urinary symptoms are present: dysuria, frequency, urgency, suprapubic pain, or flank tenderness with no alternative infection source. 1
Systemic signs of infection: fever, rigors, or hemodynamic instability attributable to urinary source. 1
Before urologic procedures: scheduled endoscopic procedures involving anticipated mucosal trauma. 1
Do NOT treat based solely on nonspecific symptoms such as malaise, fatigue, or confusion—these are more often related to underlying host factors (dehydration, electrolyte disturbances, anemia, thyroid dysfunction, depression, medication effects) rather than true urinary infection. 1
Antibiotic Selection for Symptomatic Non-Pregnant Patients
All GBS isolates worldwide remain universally susceptible to penicillin and ampicillin—no penicillin-resistant GBS has ever been documented. 4, 6
First-generation cephalosporins (cephalothin, cefazolin) show 100% susceptibility. 1
Avoid tetracycline and co-trimoxazole: GBS shows high resistance (82–88% and 69%, respectively). 4
Clindamycin resistance is significant (13–25%): always obtain susceptibility testing before use. 4, 6
Key Laboratory Considerations
Laboratories should report GBS isolated from urine at concentrations ≥10,000 CFU/mL (≥10⁴ CFU/mL) in pregnant women. 1
Inform laboratories when urine specimens are from pregnant patients to ensure appropriate reporting thresholds. 1
For high-risk penicillin-allergic pregnant patients, request clindamycin and erythromycin susceptibility testing plus D-zone testing within 3 days. 1