What is the recommended treatment for a pregnant woman with a Group B Streptococcus (GBS) urinary tract infection (UTI)?

Treatment of Group B Streptococcus UTI in Pregnancy

Pregnant women with GBS urinary tract infection at any concentration must receive immediate antibiotic treatment for the acute UTI followed by mandatory intravenous antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier in pregnancy. 1

Immediate Treatment of the Acute UTI

When GBS is detected in urine during pregnancy, treat the symptomatic infection immediately according to standard pregnancy UTI protocols:

• Penicillin-based antibiotics are preferred for treating the acute infection, though specific oral regimens are not detailed in the highest-quality guidelines 1, 2
• Ampicillin 500 mg orally three times daily for 3-7 days is a reasonable first-line option based on general UTI treatment principles 3, 4
• Alternative agents include nitrofurantoin, fosfomycin trometamol, or third-generation cephalosporins (such as cefixime) for oral therapy 5, 4

Critical Understanding: Why Intrapartum Prophylaxis is Mandatory

Treating the UTI does NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical. 1 This is why intrapartum IV prophylaxis remains absolutely mandatory even if bacteriuria was treated earlier in pregnancy. 1

GBS bacteriuria at any concentration is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 1 Women with GBS bacteriuria are heavily colonized and at increased risk of delivering an infant with early-onset GBS disease. 1

Mandatory Intrapartum Prophylaxis Regimens

For Women Without Penicillin Allergy:

• Penicillin G 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery (preferred agent due to narrow spectrum and universal GBS susceptibility) 1, 6
• Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative but broader spectrum) 1, 6

For Women With Penicillin Allergy (Not High-Risk for Anaphylaxis):

• Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery 1, 6

For Women at High Risk for Anaphylaxis:

High-risk features include history of immediate hypersensitivity reactions (anaphylaxis, angioedema, urticaria) or history of asthma that would make anaphylaxis more dangerous. 1

• Clindamycin 900 mg IV every 8 hours until delivery (if isolate confirmed susceptible—resistance ranges 3-15%) 1, 6
• Vancomycin 1 g IV every 12 hours until delivery (if isolate resistant to clindamycin or susceptibility unknown) 1, 6

Susceptibility testing for clindamycin must be performed on GBS isolates from penicillin-allergic women at high risk for anaphylaxis. 1

Timing and Effectiveness

Intrapartum prophylaxis must be administered ≥4 hours before delivery for maximum effectiveness. 1 When given ≥4 hours before delivery, prophylaxis is 78% effective in preventing early-onset neonatal GBS disease. 1

Key Management Points

• Women with GBS bacteriuria at any point during pregnancy should NOT be re-screened with vaginal-rectal cultures at 35-37 weeks—they are presumed to be GBS colonized and automatically qualify for intrapartum prophylaxis 1, 6
• Document the GBS bacteriuria clearly in the prenatal record and communicate to the anticipated site of delivery 1
• Laboratories should report GBS at concentrations ≥10,000 CFU/mL (≥10⁴ CFU/mL) when specimens are from pregnant women 1

Common Pitfalls to Avoid

The most dangerous error is assuming that treating the UTI eliminates the need for intrapartum prophylaxis. 1 This misconception can lead to failure to provide life-saving prophylaxis during labor.

Antimicrobial agents should NOT be used before the intrapartum period to eradicate GBS colonization (outside of treating acute symptomatic UTI), as such treatment is not effective in eliminating carriage or preventing neonatal disease and can cause adverse consequences including antibiotic resistance. 6, 1

Special Pregnancy Scenarios

Preterm Labor:

• Women admitted with signs and symptoms of preterm labor (<37 weeks) with GBS bacteriuria should receive GBS prophylaxis immediately at hospital admission 6, 1
• Continue prophylaxis until delivery if entering true labor; discontinue if not in true labor 6

Preterm Premature Rupture of Membranes (PPROM):

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours is adequate for both latency and GBS prophylaxis 6, 1
• At onset of labor, continue antibiotics until delivery 6