What antibiotic is recommended for a urinary tract infection (UTI) during the first trimester of pregnancy in a patient with group B streptococcus (GBS)?

Treatment of GBS UTI in First Trimester Pregnancy

For a first-trimester pregnant woman with a GBS urinary tract infection, treat immediately with penicillin G (5 million units IV initially, then 2.5 million units IV every 4 hours) or ampicillin (2 g IV initially, then 1 g IV every 4 hours), and ensure she receives intrapartum antibiotic prophylaxis during labor regardless of whether the UTI was treated earlier in pregnancy. 1

Why Immediate Treatment is Critical

• GBS bacteriuria at any concentration during pregnancy indicates heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 2, 1
• Treatment of the acute UTI does NOT eliminate GBS colonization from the genitourinary tract, and recolonization after antibiotics is typical. 2
• This patient requires both treatment of the current UTI AND intrapartum prophylaxis during labor, even if the UTI is successfully treated now. 1, 3

First-Line Antibiotic Regimens

Preferred Agent

• Penicillin G remains the agent of choice due to its narrow spectrum, universal GBS susceptibility (no documented resistance worldwide), and proven efficacy. 1, 3
• Dosing: 5 million units IV initially, then 2.5 million units IV every 4 hours until symptoms resolve 1

Acceptable Alternative

• Ampicillin (2 g IV initially, then 1 g IV every 4 hours) is an acceptable alternative but has broader spectrum activity. 1, 3

Management for Penicillin-Allergic Patients

Non-Severe Allergy (No History of Anaphylaxis, Angioedema, Respiratory Distress, or Urticaria)

• Cefazolin is the preferred alternative (2 g IV initially, then 1 g IV every 8 hours). 1, 4
• Cross-reactivity between penicillins and cephalosporins occurs in approximately 10% of patients with penicillin allergy. 4, 3

Severe Allergy (High Risk for Anaphylaxis)

• Obtain susceptibility testing for clindamycin and erythromycin immediately. 1, 4
• If susceptible: Clindamycin 900 mg IV every 8 hours 1, 4
• If resistant or testing unavailable: Vancomycin 1 g IV every 12 hours 1, 4
• Testing for inducible clindamycin resistance is necessary for isolates susceptible to clindamycin but resistant to erythromycin. 1

Critical Clinical Pitfalls to Avoid

The Recolonization Problem

• Do NOT assume that treating the UTI now eliminates the need for intrapartum prophylaxis. Antibiotics do not eliminate GBS from the genitourinary and gastrointestinal tracts. 2, 1
• Women with GBS bacteriuria during the first trimester may not have vaginal-rectal colonization detected at 35-37 weeks, but they still require intrapartum prophylaxis. 2

Documentation Requirements

• Clearly document "GBS bacteriuria in pregnancy" in the patient's chart to ensure intrapartum prophylaxis is administered during labor. 1
• Failure to provide intrapartum prophylaxis to women with previous GBS bacteriuria increases the risk of early-onset neonatal GBS disease. 1

Antibiotic Stewardship Concerns

• Avoid using oral antibiotics or treating GBS colonization outside of active infection or labor, as this is ineffective in eliminating carriage and promotes antibiotic resistance. 1, 3
• Vancomycin should be reserved for cases where no other options exist to minimize promoting antimicrobial resistance. 3

Follow-Up Management

During Pregnancy

• Complete the full prescribed course of antibiotics to ensure eradication of the acute infection. 1
• No routine GBS screening at 35-37 weeks is needed since this patient already has documented GBS bacteriuria requiring intrapartum prophylaxis. 2, 1

At Time of Labor

• Administer intrapartum antibiotic prophylaxis regardless of when the UTI was treated. 1, 3
• Use the same antibiotic regimen as for acute treatment (penicillin G or ampicillin preferred, or appropriate alternative for penicillin allergy). 1
• Prophylaxis should be administered for ≥4 hours before delivery for maximum effectiveness (78% reduction in early-onset GBS disease). 2

Special Considerations for First Trimester

• Avoid sulfonamides and nitrofurantoin in the first trimester due to potential risks of birth defects including anencephaly, heart defects, and orofacial clefts. 5
• While these agents are commonly used for other UTI pathogens, penicillins and cephalosporins are safer choices for first-trimester GBS UTI. 5