What is the recommended treatment for a 16-year-old with symptoms concerning for a Urinary Tract Infection (UTI)?

Diagnostic Testing for Suspected UTI in a 16-Year-Old

Order a urinalysis with urine culture and sensitivity testing before initiating empiric antibiotic therapy. 1

Initial Diagnostic Approach

Urine Collection and Testing

• Obtain a clean-catch midstream urine specimen for urinalysis and culture 1
• Urinalysis should include microscopy to assess for pyuria (white blood cells) and bacteriuria 2
• Urine culture is essential to confirm the diagnosis with bacterial growth ≥10^5 CFU/mL and identify the specific pathogen 2, 3
• Culture and sensitivity testing guides definitive therapy and is critical given rising antibiotic resistance rates 1, 4

Why Culture Matters in Adolescents

At 16 years old, this patient falls into the category where routine imaging is generally NOT indicated for a first uncomplicated febrile UTI 1, 5. However, culture results are crucial because:

• E. coli resistance to trimethoprim-sulfamethoxazole ranges from 19-63% in some populations 5
• Local resistance patterns vary significantly and should guide empiric choices 1, 5
• Culture allows for targeted therapy adjustment if the patient doesn't respond within 48 hours 1

Empiric Treatment While Awaiting Culture

First-Line Oral Antibiotic Options

For uncomplicated cystitis (lower UTI):

• Nitrofurantoin 100 mg twice daily for 5 days is the preferred first-line agent 1, 5, 3
• Alternative: Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days (if local resistance <20%) 1, 3
• Alternative: Fosfomycin 3 g single dose 1, 3

For pyelonephritis (upper UTI/febrile):

• First-generation cephalosporin or TMP-SMX for 7 days (based on local resistance) 1
• Ceftriaxone IV if parenteral therapy needed 1
• Fluoroquinolones for 5-7 days are effective but should be reserved for more invasive infections 1, 3

When to Use Parenteral Therapy

Reserve IV antibiotics for patients who: 5

• Appear "toxic" or septic
• Cannot retain oral intake or medications
• Have uncertain compliance with oral therapy
• Show no improvement within 48 hours of oral therapy 1, 5

Common Pitfalls to Avoid

• Do NOT treat based on dipstick alone without confirming bacteriuria 2
• Do NOT use nitrofurantoin for febrile UTI/pyelonephritis as it doesn't achieve adequate serum concentrations 5
• Do NOT prescribe antibiotics for asymptomatic bacteriuria as this promotes resistance 5
• Do NOT delay culture collection if antibiotics are started empirically 1

Follow-Up Considerations

Imaging Indications

Imaging IS indicated if: 1, 5

• Poor response to antibiotics within 48 hours
• Recurrent UTI
• Sepsis or seriously ill appearance
• Non-E. coli organism
• Elevated creatinine

Imaging is NOT routinely needed for a first uncomplicated UTI with good response to treatment in this age group 1, 5

Expected Clinical Response

• Most patients show improvement within 24-48 hours of appropriate antibiotics 5
• Adjust therapy based on culture results if no improvement or if sensitivities indicate resistance 1