Can Macrobid Treat Group B Strep UTI?
Nitrofurantoin (Macrobid) can effectively treat Group B Streptococcus urinary tract infections in pregnant women, with all GBS isolates showing susceptibility to this agent, but any pregnant woman with GBS bacteriuria at any concentration must also receive intrapartum IV antibiotic prophylaxis during labor regardless of prior treatment. 1
Treatment of the Acute UTI
Nitrofurantoin is an appropriate and effective choice for treating GBS UTI during pregnancy, as research demonstrates 100% susceptibility of GBS isolates to this antibiotic with only 2% showing intermediate sensitivity. 1
The acute UTI should be treated according to current standards of care for urinary tract infections during pregnancy using pregnancy-safe antibiotics. 2, 3
Alternative first-line options for treating the acute infection include amoxicillin 500 mg three times daily for 3 days or first-generation cephalosporins. 4, 5
Complete the full prescribed course to ensure eradication and prevent recurrence, though this will NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical. 2
Critical Requirement: Intrapartum Prophylaxis
All pregnant women with GBS bacteriuria at any concentration during any trimester of the current pregnancy must receive intrapartum IV antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier in pregnancy. 6, 2, 3
GBS bacteriuria is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 2, 3
These women do NOT need additional GBS screening at 35-37 weeks' gestation—the presence of GBS bacteriuria at any point automatically qualifies them for intrapartum prophylaxis. 3
Intrapartum Prophylaxis Regimens
For women without 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). 2
- Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative). 2
For penicillin-allergic patients not at high risk for anaphylaxis:
- Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery (preferred alternative). 2
For patients at high risk for anaphylaxis:
- Clindamycin 900 mg IV every 8 hours if the isolate is confirmed susceptible. 2
- Vancomycin 1 g IV every 12 hours if susceptibility testing unavailable or isolate resistant to clindamycin. 2
Why Both Treatments Are Necessary
Treating the UTI with oral antibiotics like nitrofurantoin addresses the acute infection but does NOT eliminate GBS colonization from the genitourinary tract—this is why intrapartum IV prophylaxis remains mandatory even after successful UTI treatment. 2
Intrapartum prophylaxis administered ≥4 hours before delivery is 78% effective in preventing early-onset neonatal GBS disease. 2
Attempting to eradicate GBS colonization before labor with repeated courses of antibiotics is ineffective and may cause adverse consequences including antibiotic resistance. 6, 3
Important Clinical Pitfalls to Avoid
Do not assume that treating the UTI eliminates the need for intrapartum prophylaxis—this is the most critical error, as GBS recolonization is typical after oral antibiotics. 2, 3
Do not withhold intrapartum prophylaxis even if subsequent cultures are negative—the history of GBS bacteriuria during the current pregnancy mandates prophylaxis. 3
Intrapartum prophylaxis is not needed only if cesarean delivery is performed before onset of labor on a woman with intact amniotic membranes. 6, 3
Context for Non-Pregnant Patients
In non-pregnant patients, GBS bacteriuria should only be treated if symptomatic or if underlying urinary tract abnormalities exist—asymptomatic bacteriuria should not be treated in this population. 7
The universal treatment mandate for any concentration of GBS in urine applies specifically to pregnant women to prevent neonatal disease and should not be applied to non-pregnant patients. 7