What is the recommended treatment for Group B Streptococcus (GBS) urinary tract infection (UTI) in pregnant women?

Treatment of Group B Streptococcus (GBS) Urinary Tract Infection in Pregnant Women

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

Immediate Treatment of the Acute UTI

First-Line Antibiotic Options

• Treat the symptomatic or asymptomatic UTI immediately with standard pregnancy-safe antibiotics such as amoxicillin 500 mg every 8 hours or penicillin VK 500 mg every 6 hours for 7-10 days 2
• Ampicillin is an acceptable alternative with proven efficacy against GBS 3
• Complete the full prescribed antibiotic course to ensure eradication and prevent recurrence 1, 4

For Penicillin-Allergic Patients

• For non-severe penicillin allergy (no history of anaphylaxis, angioedema, or urticaria): Use cephalexin 500 mg every 6 hours as the preferred alternative 2
• For high-risk allergy (history of anaphylaxis or severe immediate hypersensitivity): Use clindamycin 300-450 mg every 6 hours orally, but only if susceptibility testing confirms the isolate is susceptible 2
• Approximately 20% of GBS isolates are resistant to clindamycin, making susceptibility testing mandatory before using this agent 4

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 the following principle is absolute:

• GBS bacteriuria at any concentration during pregnancy indicates heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease 1, 5
• Women with GBS bacteriuria must receive intrapartum IV antibiotic prophylaxis during labor even if the UTI was successfully treated earlier in pregnancy 1, 2
• Failure to provide intrapartum prophylaxis increases the risk of early-onset neonatal GBS disease 1

Intrapartum Antibiotic Prophylaxis During Labor

First-Line Regimen

• Penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery is the preferred agent due to its narrow spectrum and universal GBS susceptibility 6, 1
• Ampicillin 2 g IV initial dose, then 1 g IV every 4 hours is an acceptable alternative but has broader spectrum activity 6, 1
• Administer prophylaxis ≥4 hours before delivery for maximum effectiveness (78% reduction in early-onset neonatal GBS disease) 1

For Penicillin-Allergic Patients During Labor

• Not at high risk for anaphylaxis: Cefazolin 2 g IV initially, then 1 g IV every 8 hours 1, 2
• At high risk for anaphylaxis: Clindamycin 900 mg IV every 8 hours (if susceptible) or vancomycin 1 g IV every 12 hours 1, 2
• Susceptibility testing for clindamycin and erythromycin must be performed on GBS isolates from penicillin-allergic women at high risk for anaphylaxis 1
• Testing for inducible clindamycin resistance is necessary for isolates susceptible to clindamycin but resistant to erythromycin 1, 4

Special Clinical Scenarios

Preterm Labor or PPROM

• Women admitted with signs of preterm labor with positive GBS screen should receive GBS prophylaxis immediately at hospital admission 1
• For women with 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

Laboratory Reporting Threshold

• Laboratories should report GBS present at ≥10,000 CFU/mL (≥10^4 CFU/mL) as clinically significant in pregnancy 1
• Any concentration of GBS in urine during pregnancy requires treatment and intrapartum prophylaxis 1

Critical Pitfalls to Avoid

• Do NOT attempt to "decolonize" the patient with prolonged antibiotic courses outside of treating active infection—this is ineffective and promotes antibiotic resistance 1, 2
• Do NOT use antimicrobial agents before the intrapartum period to treat asymptomatic GBS colonization—such treatment does not eliminate carriage or prevent neonatal disease 6, 1
• Do NOT underdose or allow premature discontinuation of therapy, as this leads to treatment failure and recurrence 1, 4
• Do NOT forget that intrapartum prophylaxis is mandatory even if the UTI was treated months earlier in pregnancy 1, 2
• The estimated frequency of anaphylactic reactions to penicillin is approximately 4-40 per 10,000 recipients, making allergy history assessment critical 6, 7