What is the treatment for a urinary tract infection (UTI) with a urinalysis positive for nitrates and leukocytes?

Treatment of Urinary Tract Infection with Positive Nitrites and Leukocytes

First-line treatment for a urinary tract infection with positive nitrites and leukocytes includes nitrofurantoin, trimethoprim-sulfamethoxazole (when local resistance is <20%), or fosfomycin, with nitrofurantoin being the preferred option due to lower resistance rates. 1

Diagnostic Interpretation

When urinalysis shows positive nitrites and leukocytes, this strongly suggests a urinary tract infection:

• The combination of positive leukocyte esterase and nitrites has a sensitivity of 93% and specificity of 72% for UTI 1
• Nitrites are highly specific (98%) but less sensitive (53%) for UTI 1
• Leukocyte esterase has moderate sensitivity (83%) and specificity (78%) 1

It's important to note that while these findings strongly suggest UTI, the diagnosis should be made in conjunction with clinical symptoms such as dysuria, frequency, urgency, and suprapubic pain.

Treatment Algorithm

1. First-line Antibiotic Options:

• Nitrofurantoin (preferred first-line):

  • Dosage: 100 mg twice daily for 5 days
  • Advantages: Low resistance rates, minimal collateral damage 2
  • Contraindications: CrCl <30 mL/min, G6PD deficiency

• Trimethoprim-sulfamethoxazole (TMP-SMX):

  • Dosage: 160/800 mg (1 DS tablet) twice daily for 3 days
  • Use when local resistance is <20% 2
  • FDA-approved for UTIs caused by susceptible strains of E. coli, Klebsiella, Enterobacter, Morganella morganii, and Proteus species 3

• Fosfomycin:

  • Dosage: 3 g single dose
  • Convenient single-dose therapy 1

2. Special Considerations:

• For complicated UTIs (males, pregnancy, immunocompromised, abnormal urinary tract, symptoms >7 days):

  • Obtain urine culture before starting antibiotics 1
  • Consider broader spectrum antibiotics pending culture results
  • Longer treatment duration (7-14 days)

• For recurrent UTIs:

  • Always obtain culture before starting antibiotics 1
  • Consider non-antimicrobial preventive measures such as methenamine hippurate, probiotics, or cranberry products 1

3. Follow-up:

• Instruct patients to return if symptoms persist after 48-72 hours of treatment
• No need for repeat urinalysis if symptoms resolve 1
• Advise patients to seek prompt medical evaluation (within 48 hours) for future febrile illnesses 1

Common Pitfalls to Avoid

1. Treating asymptomatic bacteriuria: Positive nitrites and leukocytes without symptoms should not be treated in most populations, as this increases antimicrobial resistance without reducing morbidity 1

2. Ignoring local resistance patterns: Local resistance to TMP-SMX can be high in some areas, making it less effective as empiric therapy 2

3. Inadequate specimen collection: Urine should be processed within 2 hours or refrigerated to prevent false results 1

4. Overlooking the need for culture in complicated cases: Always obtain culture before starting antibiotics in complicated UTIs, recurrent infections, or treatment failures 1

5. Misinterpreting pyuria: Pyuria indicates inflammation but can be present in many non-infectious conditions 1

By following this evidence-based approach to treating UTIs with positive nitrites and leukocytes, you can provide effective therapy while practicing good antimicrobial stewardship.