Should This Patient Continue Bactrim?
Stop the Bactrim immediately—this patient has sterile pyuria (trace leukocytes with negative culture), and continuing antibiotics provides no benefit while increasing risks of adverse effects, C. difficile infection, and antimicrobial resistance. 1, 2
Clinical Reasoning
This is Sterile Pyuria, Not a UTI
The negative urine culture after 3 days definitively rules out bacterial cystitis requiring antibiotic treatment. 1 The presence of pyuria (trace leukocytes) with negative culture is common and does not indicate bacterial infection requiring antibiotics. 3
- Pyuria alone is not an indication for antimicrobial treatment, even when accompanied by urinary symptoms. 3
- The trace hematuria and urinary symptoms with sterile pyuria indicate urinary tract inflammation from a non-bacterial cause. 1
Why Continuing Antibiotics is Harmful
The IDSA explicitly recommends against treating asymptomatic bacteriuria or sterile pyuria in elderly patients due to:
- Increased risk of C. difficile infection 2
- Development of antimicrobial resistance 2
- Adverse drug reactions (particularly concerning in elderly patients) 2, 4
- No improvement in symptoms or outcomes 3, 5
The FDA label for Bactrim specifically warns of increased risk of severe adverse reactions in elderly patients, including severe skin reactions, bone marrow suppression, thrombocytopenia, and hyperkalemia. 4
What to Do Instead
Evaluate for non-bacterial causes of sterile pyuria: 1
- Sexually transmitted infections (urethritis from chlamydia/gonorrhea)
- Urolithiasis (kidney stones)
- Interstitial cystitis
- Fungal infection (especially if recent antibiotic use or immunocompromised)
- Tuberculosis (if risk factors present)
- Prostatitis (in males)
Obtain renal/bladder ultrasound to evaluate for stones or anatomic abnormalities. 1
Consider STI testing if sexually active, as urethritis commonly presents with dysuria and frequency but negative standard urine culture. 1
Critical Pitfall to Avoid
Do not dismiss this as "asymptomatic bacteriuria"—the presence of symptoms (burning, frequency, urgency) with pyuria indicates true inflammation requiring investigation, not antibiotics. 1 The culture being negative means the inflammation is from a non-bacterial cause that standard UTI antibiotics will not address. 1
When to Reconsider Antibiotics
Only restart antibiotics if: 1, 2
- Fever develops (temperature >38°C/100.4°F)
- Signs of systemic infection/urosepsis appear (hemodynamic instability, altered mental status)
- Flank pain develops suggesting pyelonephritis
- A specific pathogen is identified on specialized testing (STI, fungal, TB cultures)