What is the recommended treatment for urinary tract infections (UTIs) in infants?

Treatment of Urinary Tract Infections in Infants

For febrile infants 2-24 months with UTI, initiate oral antibiotics for 7-14 days with amoxicillin-clavulanate, a cephalosporin, or trimethoprim-sulfamethoxazole based on local resistance patterns, reserving parenteral therapy only for toxic-appearing infants or those unable to retain oral medications. 1, 2

Initial Treatment Selection by Age and Clinical Presentation

Neonates (<28 days)

• Hospitalize all neonates and administer parenteral therapy with ampicillin plus either an aminoglycoside (gentamicin) or third-generation cephalosporin (ceftazidime or cefotaxime) for 14 days total 3, 4
• After 3-4 days of parenteral therapy with good clinical response, transition to oral antibiotics to complete the 14-day course 3

Young Infants (29 days to 3 months)

• For toxic-appearing or clinically ill infants: Hospitalize and give parenteral ceftriaxone (50 mg/kg every 24 hours) or gentamicin until afebrile for 24 hours, then complete 14 days total with oral antibiotics 2, 3, 4
• For well-appearing, stable infants: May treat as outpatients with either parenteral ceftriaxone/gentamicin daily until afebrile for 24 hours, then oral antibiotics to complete 14 days, OR initiate oral cephalosporin (cephalexin 50-100 mg/kg/day in 4 doses or cefixime 8 mg/kg/day in 1 dose) 1, 2, 3

Infants and Children (3-24 months)

• Most can be treated with oral antibiotics from the start unless they appear toxic, cannot retain oral intake, or compliance is uncertain 1, 2
• First-line oral options include:
  • Amoxicillin-clavulanate: 20-40 mg/kg/day in 3 divided doses 1, 2, 5
  • Cephalexin: 50-100 mg/kg/day in 4 doses 1, 2
  • Cefixime: 8 mg/kg/day in 1 dose 1, 6
  • Cefpodoxime: 10 mg/kg/day in 2 doses 1
  • Trimethoprim-sulfamethoxazole (if local resistance <10% for pyelonephritis) 2, 5

Treatment Duration

• Febrile UTI/pyelonephritis requires 7-14 days total therapy regardless of whether initial route is oral or parenteral 1, 2, 5
• Courses shorter than 7 days are inferior and should not be used for febrile UTIs 1, 5
• For infants initially requiring parenteral therapy, switch to oral antibiotics once clinically improved (typically within 24-48 hours) to complete the full course 1, 2, 5

Critical Antibiotic Selection Considerations

Local Resistance Patterns

• Always consider local antimicrobial resistance data when selecting empiric therapy, as there is substantial geographic variability in resistance to trimethoprim-sulfamethoxazole and cephalexin 1, 2, 5
• Trimethoprim-sulfamethoxazole should only be used if local resistance rates are <10% for pyelonephritis 2, 5

Agents to Avoid in Febrile Infants

• Never use nitrofurantoin for febrile UTIs because it does not achieve adequate serum or parenchymal concentrations to treat pyelonephritis or urosepsis, despite achieving urinary concentrations 1, 2, 5
• Avoid fluoroquinolones in children due to musculoskeletal safety concerns; reserve only for severe infections where benefits outweigh risks 2, 5

Indications for Parenteral Therapy

• Toxic appearance or hemodynamic instability 1, 4
• Age <28 days (always) 3, 4
• Inability to retain oral fluids or medications 1, 2
• Uncertain compliance with obtaining or administering oral antibiotics 1
• Immunocompromised status 4
• Lack of response to oral therapy 4

Follow-Up and Monitoring

Short-Term Follow-Up (1-2 Days)

• Clinical reassessment within 1-2 days is critical to confirm response to antibiotics and fever resolution 2
• If fever persists beyond 48 hours of appropriate therapy, reevaluate for antibiotic resistance or anatomic abnormalities 2

Imaging Recommendations

• Obtain renal and bladder ultrasonography (RBUS) for all febrile infants <2 years with first UTI to detect anatomic abnormalities requiring further evaluation 1, 2, 5
• RBUS timing: For clinically improving infants, imaging can be performed after acute phase; for severely ill infants or those not improving, perform within first 2 days to identify complications like abscess or obstruction 1
• Voiding cystourethrography (VCUG) is NOT recommended routinely after first UTI 1, 2, 5
• Perform VCUG only if: RBUS shows hydronephrosis, scarring, or findings suggesting high-grade vesicoureteral reflux or obstruction, OR after a second febrile UTI 1, 2, 5

Long-Term Follow-Up

• No routine scheduled visits necessary after successful treatment of uncomplicated first UTI 2, 5
• Instruct parents to seek prompt evaluation (within 48 hours) for any future febrile illness to detect recurrent UTIs early 2

Common Pitfalls to Avoid

• Do not delay antibiotic treatment when febrile UTI is suspected, as early treatment (ideally within 48 hours of fever onset) may reduce risk of renal scarring 2
• Do not use nitrofurantoin for any febrile infant with suspected pyelonephritis 1, 2, 5
• Do not treat for less than 7 days for febrile UTIs 1, 5
• Do not fail to adjust therapy based on culture and sensitivity results when available 2, 5
• Do not treat asymptomatic bacteriuria 2, 5
• Do not perform surveillance urine cultures in asymptomatic patients 5

Antibiotic Prophylaxis Considerations

• Routine antimicrobial prophylaxis is NOT recommended after first UTI in infants without vesicoureteral reflux or with grades I-IV VUR 1, 2
• Consider prophylaxis only in select high-risk patients with recurrent febrile UTIs, high-grade VUR (grades IV-V), or bowel and bladder dysfunction 2, 5
• The RIVUR trial showed prophylaxis reduced recurrent UTI by approximately 50% in children with VUR grades I-IV but did not reduce renal scarring 2