What oral antibiotic can be given to a pregnant patient in the first trimester with Group B streptococci (GBS) bacteriuria and a urine culture showing 50,000-100,000 colony-forming units (CFU), who is allergic to Zosyn (Piperacillin/Tazobactam)?

Treatment of GBS Bacteriuria in First Trimester Pregnancy with Zosyn Allergy

For a pregnant patient in the first trimester with Group B streptococcal bacteriuria (50,000-100,000 CFU) who is allergic to Zosyn, oral amoxicillin-clavulanic acid is the recommended first-line oral treatment option. 1

Antibiotic Selection Algorithm

1. First-line oral option: Amoxicillin-clavulanic acid

   • Recommended by WHO as a first-choice option for GBS urinary tract infections 1
   • Safe in pregnancy, especially first trimester

2. Alternative options (if amoxicillin-clavulanic acid cannot be used):

   • Nitrofurantoin

     • Effective against GBS and commonly used in pregnancy 1, 2
     • Note: While there were previous concerns about potential birth defects, it remains a recommended option when other antibiotics are inappropriate 3

   • Cephalexin (first-generation cephalosporin)

     • Safe in pregnancy and effective against GBS 1, 3
     • Good option if patient doesn't have severe penicillin allergy with anaphylaxis

3. If severe penicillin allergy with anaphylaxis history:

   • Clindamycin (if susceptibility testing confirms sensitivity)
     • Important: GBS has 14-26.6% resistance rates to clindamycin 1
     • Susceptibility testing is essential before using

Important Clinical Considerations

• GBS bacteriuria significance: Any concentration of GBS in urine during pregnancy is a marker for heavy genital tract colonization and increases risk for early-onset GBS disease in the newborn 4, 1

• Colony count threshold: The patient's count of 50,000-100,000 CFU meets the significant bacteriuria threshold (>10^5 CFU/ml) associated with increased risk of early-onset GBS disease 4

• Treatment timing: Treat GBS bacteriuria immediately upon diagnosis, regardless of trimester 1

• Follow-up: After completing the antibiotic course:

  • Obtain a test of cure urine culture
  • Plan for intrapartum antibiotic prophylaxis during labor regardless of subsequent negative cultures 4, 1

Cautions and Pitfalls

• Avoid oral trimethoprim-sulfamethoxazole in first trimester due to potential risk for birth defects including anencephaly, heart defects, and orofacial clefts 3

• Avoid fluoroquinolones (like ciprofloxacin) in pregnancy unless absolutely necessary 1, 3

• Antibiotic resistance: Be aware that ampicillin alone has high resistance rates to common uropathogens including E. coli 5

• Duration of therapy: A 7-day regimen of antibiotics provides better microbiological cure rates than shorter courses 6

• Recolonization risk: Despite antibiotic treatment during pregnancy, recolonization after a course of antibiotics is typical, which is why intrapartum prophylaxis is still required 4

• Allergic reaction monitoring: Carefully monitor for allergic reactions, especially with beta-lactam antibiotics in a patient with known Zosyn allergy

Remember that treating GBS bacteriuria during pregnancy is essential to prevent complications including pyelonephritis, preterm labor, and neonatal sepsis 4, 1, 5.