What is the recommended treatment—including first‑line antibiotic, dosage, duration, and alternatives for penicillin allergy or renal impairment—for a symptomatic adult or pregnant patient with a Group B Streptococcus (GBS)‑positive urine culture?

Treatment of Group B Streptococcus Positive Urine Culture

For pregnant women with GBS bacteriuria at any concentration, treat the acute UTI immediately with standard pregnancy-safe antibiotics and provide mandatory intravenous intrapartum antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier in pregnancy. 1

Pregnancy Context: Critical Two-Step Management

Step 1: Immediate Treatment of the UTI

First-line antibiotic options for treating the acute GBS UTI:

• Nitrofurantoin 100 mg orally twice daily for 7 days is the preferred first-line agent for lower UTI 2
• Cephalexin 500 mg orally four times daily for 7–14 days is an excellent alternative, particularly if upper tract involvement is suspected 1, 2
• Fosfomycin 3 g single oral dose can be used for uncomplicated lower UTI 2
• Ampicillin 500 mg orally four times daily for 7 days is acceptable if susceptibility is confirmed 1

Duration: 7–14 days for symptomatic UTI; minimum 7 days for asymptomatic bacteriuria 3, 2

Critical caveat: Treating the UTI 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

Step 2: Mandatory Intrapartum Prophylaxis During Labor

All pregnant women with GBS bacteriuria at ANY concentration during ANY trimester must receive IV antibiotic prophylaxis during labor. 3, 1 GBS bacteriuria is a marker for heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease. 3, 1

Preferred intrapartum regimen (no penicillin allergy):

• Penicillin G 5 million units IV initially, then 2.5–3.0 million units IV every 4 hours until delivery 3, 1, 4
• Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery is an acceptable alternative 3, 1

Timing is critical: Administer antibiotics at least 4 hours before delivery for maximum effectiveness—this achieves a 78–89% reduction in early-onset neonatal GBS disease. 3, 1, 4

Penicillin-Allergic Patients

For low-risk penicillin allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):

• Cefazolin 2 g IV initially, then 1 g IV every 8 hours until delivery 3, 1, 4

For high-risk penicillin allergy (history of anaphylaxis or severe immediate hypersensitivity):

• Obtain susceptibility testing for clindamycin and erythromycin on the GBS isolate 3, 1
• If susceptible to both: Clindamycin 900 mg IV every 8 hours until delivery 3, 1, 4
• If resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery 3, 1, 4
• Perform D-zone testing on isolates that are erythromycin-resistant but clindamycin-susceptible to detect inducible clindamycin resistance 3, 1

Important note: Clindamycin resistance ranges from 13–25% among GBS isolates, making susceptibility testing essential. 1, 5

Special Pregnancy Scenarios

Preterm labor (<37 weeks) with GBS bacteriuria:

• Initiate GBS prophylaxis immediately at hospital admission 1
• Discontinue if the patient is not in true labor 3, 1

Preterm premature rupture of membranes (PPROM):

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours provides both latency prolongation and adequate GBS prophylaxis 3, 1

Documentation and Screening Exemption

• Women with documented GBS bacteriuria at any point during pregnancy should NOT be re-screened with vaginal-rectal cultures at 36–37 weeks 3, 1
• They are presumed to be heavily colonized and automatically qualify for intrapartum prophylaxis 3, 1
• Ensure laboratory reports of GBS bacteriuria are communicated to both the anticipated site of delivery and the ordering provider 1

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Non-Pregnant Adult Context

Do NOT treat asymptomatic GBS bacteriuria in non-pregnant adults. 3, 1

When Treatment IS Indicated in Non-Pregnant Patients

• Symptomatic UTI with classic urinary symptoms (dysuria, frequency, urgency, suprapubic pain) or systemic signs (fever, rigors) 1
• Before urologic procedures involving mucosal trauma or bleeding 3, 1

When Treatment Is NOT Indicated

• Asymptomatic bacteriuria in premenopausal, non-pregnant women 3
• Diabetic patients with asymptomatic bacteriuria 3, 1
• Elderly or institutionalized individuals with asymptomatic bacteriuria 3, 1
• Patients with indwelling catheters (short-term or long-term) 3, 1
• Patients with neurogenic bladder on intermittent catheterization 1
• Patients presenting only with nonspecific symptoms (malaise, fatigue) without urinary symptoms 1

Rationale: Treating asymptomatic bacteriuria leads to unnecessary antibiotic exposure, increased antimicrobial resistance, and adverse drug effects (including Clostridioides difficile infection) without clinical benefit. 3, 1

Treatment Regimens for Symptomatic Non-Pregnant Adults

First-line options:

• Cephalexin or other first-generation cephalosporins (100% susceptibility documented) 1
• Ampicillin if susceptibility is confirmed 3
• Penicillin remains universally effective against GBS 1, 5

Duration: 7–14 days for symptomatic UTI 2

Avoid: Nitrofurantoin for upper tract infections (does not achieve therapeutic blood concentrations) 2

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Critical Pitfalls to Avoid

• Never assume that treating a GBS UTI in pregnancy eliminates the need for intrapartum prophylaxis—this is a common and dangerous error. 1
• Do not use oral antibiotics before labor to treat asymptomatic GBS colonization—this is completely ineffective at eliminating carriage and promotes antibiotic resistance. 3, 1, 4
• Do not treat asymptomatic GBS bacteriuria in non-pregnant adults—this leads to unnecessary antibiotic exposure and resistance without benefit. 3, 1
• Do not delay intrapartum prophylaxis while awaiting culture results in women with risk factors (preterm labor, prolonged rupture of membranes, intrapartum fever). 3, 1
• Do not use nitrofurantoin for suspected pyelonephritis or upper tract infection in pregnancy—it does not achieve adequate blood levels. 2

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Antibiotic Susceptibility Data

• Universal susceptibility: All GBS isolates are susceptible to penicillin, ampicillin, and vancomycin 1, 5
• High resistance rates: Clindamycin (13–77%) and tetracycline (88%) 1, 5
• First-generation cephalosporins: 100% susceptibility 1