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

Treatment of Group B Streptococcus Urinary Tract Infection in Pregnant Women

Pregnant women with Group B streptococcus detected in urine at any concentration must receive immediate antibiotic treatment for the 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

• Treat the symptomatic or asymptomatic GBS UTI immediately according to standard pregnancy UTI protocols using pregnancy-safe antibiotics based on susceptibility testing. 1
• GBS bacteriuria at any concentration during pregnancy is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 1, 2
• Critical pitfall: Treating the UTI during pregnancy does NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical, which is why intrapartum IV prophylaxis remains mandatory even if bacteriuria was treated earlier in pregnancy. 1

Mandatory Intrapartum Antibiotic Prophylaxis

All pregnant women with GBS bacteriuria at any point during the current pregnancy must receive intrapartum IV antibiotic prophylaxis during labor, regardless of when or if the UTI was treated. 1, 2

First-Line Regimens (No Penicillin Allergy)

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery (preferred agent due to narrow spectrum and high efficacy). 1, 2
• Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative). 1, 2

Penicillin-Allergic Patients

For patients NOT at high risk for anaphylaxis:

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

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

• Clindamycin: 900 mg IV every 8 hours until delivery (if isolate is confirmed susceptible). 1
• Vancomycin: 1 g IV every 12 hours until delivery (if susceptibility testing unavailable or isolate resistant to clindamycin). 1
• Susceptibility testing for clindamycin and erythromycin must be performed on GBS isolates from penicillin-allergic women at high risk for anaphylaxis, as resistance to clindamycin ranges from 3-15% in GBS isolates. 1

Timing and Effectiveness

• Intrapartum prophylaxis must be administered ≥4 hours before delivery for maximum effectiveness. 1, 2
• When given ≥4 hours before delivery, prophylaxis is 78% effective in preventing early-onset neonatal GBS disease. 1, 3
• Although shorter durations are less effective, even 2 hours of antibiotic exposure has been shown to reduce GBS vaginal colony counts and decrease the frequency of clinical neonatal sepsis. 3
• Obstetric interventions should not be delayed solely to provide 4 hours of antibiotic administration before birth. 3

Additional Management Considerations

• Women with documented GBS bacteriuria should NOT be re-screened with vaginal-rectal cultures at 35-37 weeks gestation, as they are presumed to be GBS colonized and automatically qualify for intrapartum prophylaxis. 1, 2, 4
• Laboratories should be informed when urine specimens are from pregnant women so they report GBS at concentrations ≥10,000 CFU/mL (≥10^4 CFU/mL). 1
• Ensure that laboratory reports of GBS bacteriuria are communicated to both the anticipated site of delivery and the ordering provider. 1

Common Pitfalls to Avoid

• Never assume that treating the UTI eliminates the need for intrapartum prophylaxis—this is a common and dangerous error. 1
• Do not attempt to eradicate GBS colonization before labor with antibiotics, as this is ineffective and may cause adverse consequences including antibiotic resistance. 1, 2
• Do not withhold intrapartum prophylaxis for women with history of GBS bacteriuria in the current pregnancy, even if subsequent cultures are negative. 2