How should group B Streptococcus (Streptococcus agalactiae) isolated from urine be managed and treated in a pregnant or symptomatic woman?

Management of Group B Streptococcus in Urine

If you are pregnant, any concentration of GBS in urine—regardless of symptoms—requires immediate antibiotic treatment of the UTI plus mandatory intravenous antibiotic prophylaxis during labor. 1, 2 If you are not pregnant and have no urinary symptoms, no treatment is indicated. 3, 4

For Pregnant Women

Immediate Treatment Required

• Treat the acute UTI immediately with pregnancy-safe antibiotics according to standard UTI protocols, using penicillin G or ampicillin as first-line agents. 2, 4

• GBS bacteriuria at any concentration during any trimester is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 1, 2

• Treating the UTI today does not eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical. 2

Mandatory Intrapartum Prophylaxis

All pregnant women with GBS bacteriuria at any point during the current pregnancy must receive intravenous antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier. 1, 2, 4

Standard Regimen (No Penicillin Allergy)

• Penicillin G 5 million units IV initially, then 2.5–3.0 million units IV every 4 hours until delivery is the preferred agent. 1, 2

• Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery is an acceptable alternative. 1, 2

• Administer prophylaxis at least 4 hours before delivery for maximum effectiveness—this achieves a 78% reduction in early-onset neonatal GBS disease. 1, 2

Penicillin-Allergic Patients

• For low-risk allergy (no history of anaphylaxis, angioedema, or urticaria): Use cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery. 1, 2

• For high-risk allergy (history of anaphylaxis or severe immediate reactions): Obtain clindamycin and erythromycin susceptibility testing immediately. 1, 2

  • If susceptible to both: Clindamycin 900 mg IV every 8 hours until delivery. 1, 2

  • If resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery. 1, 2

• Clindamycin resistance ranges from 13–25% in GBS isolates, making susceptibility testing essential before use. 4, 5

Additional Pregnancy Considerations

• Women with GBS bacteriuria do not need vaginal-rectal screening cultures at 35–37 weeks—they automatically qualify for intrapartum prophylaxis. 1, 4

• For preterm labor (<37 weeks): Start GBS prophylaxis immediately at hospital admission; discontinue if not in true labor. 2

• For preterm premature rupture of membranes (PPROM): Ampicillin 2 g IV once, then 1 g IV every 6 hours for at least 48 hours provides both latency support and adequate GBS prophylaxis. 2

For Non-Pregnant Adults

When Treatment Is NOT Indicated

Asymptomatic GBS bacteriuria in non-pregnant adults should not be treated. 3, 4 This represents asymptomatic bacteriuria that does not require antibiotics. 3

• The 2019 IDSA guidelines provide strong evidence against treating asymptomatic bacteriuria in non-pregnant populations, including patients with diabetes, elderly individuals, and those with indwelling catheters. 3

• Treating asymptomatic bacteriuria leads to unnecessary antibiotic exposure, antimicrobial resistance, adverse drug effects, and increased risk of Clostridioides difficile infection without clinical benefit. 3

When Treatment IS Indicated

Treat GBS bacteriuria in non-pregnant adults only if:

• The patient has symptomatic UTI with classic urinary symptoms (dysuria, frequency, urgency, suprapubic pain, flank tenderness). 3, 4

• The patient has systemic signs of infection (fever, rigors, hemodynamic instability). 3

• The patient has underlying urinary tract abnormalities—60% of non-pregnant adults with GBS bacteriuria have structural urinary problems. 6

• The patient is scheduled for endoscopic urologic procedures involving mucosal trauma. 3

Treatment Regimens for Symptomatic Non-Pregnant Patients

• Penicillin G 500 mg orally every 6–8 hours for 7–10 days is the preferred agent due to narrow spectrum activity. 3

• Ampicillin 500 mg orally every 8 hours for 7–10 days is an acceptable alternative. 3

• For penicillin-allergic patients: Clindamycin 300–450 mg orally every 8 hours, with susceptibility testing performed before use. 3

• For complicated infections or when prostatitis cannot be excluded in men: Extend treatment to 14 days. 3

• For severe presentations or complicated UTI: Consider initial IV therapy with ampicillin 2 g IV every 4–6 hours, then transition to oral therapy once clinically stable. 3

Critical Pitfalls to Avoid

• Never treat asymptomatic GBS vaginal or urethral colonization with oral or IV antibiotics before labor in pregnant women—this is completely ineffective at eliminating carriage, promotes antibiotic resistance, and does not prevent neonatal disease. 1, 2

• Do not assume that treating a GBS UTI during pregnancy eliminates the need for intrapartum prophylaxis—this is a common and dangerous error. 2

• All GBS isolates are universally susceptible to penicillin and ampicillin, but resistance to clindamycin (13–25%) and erythromycin (7–21%) is significant. 4, 5

• In non-pregnant patients, do not treat GBS bacteriuria based solely on nonspecific symptoms (malaise, fatigue, confusion) without classic urinary symptoms—evaluate alternative causes instead. 3