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

Treatment of Group B Streptococcal UTI in Pregnant Women

All pregnant women with GBS bacteriuria at any concentration during any trimester must receive immediate antibiotic treatment for the acute UTI AND mandatory intrapartum IV antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier in pregnancy. 1

Immediate Treatment of the Acute UTI

For symptomatic or asymptomatic GBS UTI detected during pregnancy, treat the acute infection immediately according to standard pregnancy UTI protocols: 1

• Oral regimens for outpatient treatment:

  • Amoxicillin 500 mg every 8 hours for 7-10 days 2
  • Penicillin VK 500 mg every 6 hours for 7-10 days 2
  • Cephalexin 500 mg every 6 hours for 7-10 days (alternative for non-severe penicillin allergy) 2

• For penicillin-allergic patients at high risk for anaphylaxis:

  • Clindamycin 300-450 mg every 6 hours orally, but ONLY if susceptibility testing confirms the isolate is susceptible 2
  • Susceptibility testing must be performed on GBS isolates from penicillin-allergic patients at high risk for anaphylaxis 1

Critical Understanding: Why Intrapartum Prophylaxis is Still Required

Treating the UTI during pregnancy does NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical. 1 This is why intrapartum IV prophylaxis remains 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

Mandatory Intrapartum IV Antibiotic Prophylaxis During Labor

All pregnant women with GBS bacteriuria at ANY point during the current pregnancy must receive intrapartum antibiotic prophylaxis during labor: 1

First-Line Intrapartum Regimens (No Penicillin Allergy):

• Penicillin G (preferred): 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery 1, 3
• Ampicillin (acceptable alternative): 2 g IV initially, then 1 g IV every 4 hours until delivery 1

Penicillin G is preferred due to its narrow spectrum of activity, universal GBS susceptibility, and proven efficacy. 1

Alternative Intrapartum Regimens for Penicillin Allergy:

For patients NOT at high risk for anaphylaxis:

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery 1, 3

For patients at HIGH risk for anaphylaxis (history of immediate hypersensitivity reactions, anaphylaxis, angioedema, urticaria, or asthma):

• Clindamycin: 900 mg IV every 8 hours until delivery (if isolate is confirmed susceptible to both clindamycin and erythromycin) 1, 3
• Vancomycin: 1 g IV every 12 hours until delivery (if susceptibility is unknown or isolate is resistant to clindamycin) 1, 3

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, 3

Special Pregnancy Scenarios

Preterm Labor (<37 weeks):

• Women admitted with signs and symptoms of preterm labor with GBS bacteriuria should receive GBS prophylaxis immediately at hospital admission 1
• If the patient is determined not to be in true labor, discontinue GBS prophylaxis 4

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 4, 1

Critical Clinical Pitfalls to Avoid

• Never assume that treating the UTI eliminates the need for intrapartum prophylaxis—this is a common and dangerous error. 1 Women with GBS bacteriuria are presumed to be heavily colonized and automatically qualify for intrapartum prophylaxis regardless of UTI treatment. 1

• Do NOT attempt to "decolonize" the patient with prolonged antibiotic courses outside of treating active infection—oral or IV antibiotics given before labor are completely ineffective at eliminating GBS colonization and may cause adverse consequences including antibiotic resistance. 1, 2

• Do NOT re-screen with vaginal-rectal cultures at 35-37 weeks—women with documented GBS bacteriuria at any point in pregnancy are presumed to be GBS colonized and do not need repeat screening. 1

• Ensure laboratory reports of GBS bacteriuria are communicated to both the anticipated site of delivery and the ordering provider to prevent failure of intrapartum prophylaxis. 1

Laboratory Considerations

Laboratories should report GBS present at ≥10,000 CFU/mL (≥10⁴ CFU/mL) as the threshold for clinical significance in pregnancy. 1 However, even lower concentrations of GBS in urine warrant treatment and intrapartum prophylaxis, as they can be associated with vaginal-rectal colonization. 1