What is the best antibiotic treatment for group B streptococcal (GBS) bacteriuria in pregnancy?

Antibiotic Treatment for Group B Streptococcal Bacteriuria in Pregnancy

For pregnant women with Group B streptococcal (GBS) bacteriuria, penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery) or ampicillin (2g IV initial dose, then 1g IV every 4 hours until delivery) is the recommended first-line treatment. 1

Initial Treatment Approach

The management of GBS bacteriuria in pregnancy requires prompt treatment regardless of colony count. According to CDC guidelines, women with GBS isolated from urine at any time during pregnancy should:

1. Receive treatment for the urinary tract infection according to current standards of care 2
2. Receive intrapartum antibiotic prophylaxis (IAP) during labor to prevent early-onset GBS disease 2, 1

First-line Treatment Options:

• Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery 1
• Ampicillin: 2g IV initial dose, then 1g IV every 4 hours until delivery 1

Management for Penicillin-Allergic Patients

For patients with penicillin allergy, the treatment depends on the severity of the allergy:

• Non-anaphylactic penicillin allergy: Cefazolin 2g IV initial dose, then 1g IV every 8 hours 1
• Severe penicillin allergy (anaphylaxis, angioedema, respiratory distress):
  • If GBS is susceptible: Clindamycin 900mg IV every 8 hours 1
  • If clindamycin resistance is documented or susceptibility is unknown: Vancomycin 1g IV every 12 hours 1
• For patients with penicillin allergy and urine culture positive for both GBS and gram-negative rods: Fluoroquinolones are preferred due to their broad spectrum coverage and safety profile 1

Duration of Treatment

• Standard duration for uncomplicated cases is 7-10 days 1
• Extended therapy (14 days or longer) is recommended for slow clinical response or undrainable foci of infection 1

Important Considerations

1. No re-screening needed: Women with documented GBS bacteriuria should not be re-screened by genital tract culture or urinary culture in the third trimester, as they are presumed to be GBS colonized 3

2. Intrapartum prophylaxis: All women with GBS bacteriuria during the current pregnancy must receive intrapartum antibiotic prophylaxis during labor, regardless of whether they received treatment earlier in pregnancy 2, 4

3. Colony count considerations: While standard practice is to treat bacteriuria with ≥100,000 CFU/mL, the CDC guidelines recommend treating GBS bacteriuria in pregnancy regardless of colony count 2, 3

4. Delivery considerations: Intrapartum antibiotic prophylaxis is not indicated if a cesarean delivery is performed before onset of labor on a woman with intact amniotic membranes 2

Common Pitfalls to Avoid

• Failure to provide intrapartum prophylaxis: Even if GBS bacteriuria was successfully treated earlier in pregnancy, intrapartum prophylaxis is still required 2, 4

• Unnecessary re-screening: Once GBS bacteriuria is documented, the patient is considered GBS colonized for the remainder of the pregnancy and does not need repeat screening 3

• Inadequate duration of intrapartum prophylaxis: Optimal IAP should be administered for at least 4 hours before delivery, though even 2 hours of antibiotic exposure has been shown to reduce GBS vaginal colony counts 1

• Overlooking asymptomatic bacteriuria: GBS bacteriuria may be asymptomatic but still requires treatment and intrapartum prophylaxis 5

By following these evidence-based guidelines, clinicians can effectively manage GBS bacteriuria in pregnancy and reduce the risk of maternal and neonatal complications.