Treatment of Urinary Tract Infection with Bacteria on Urinalysis
For a patient with symptomatic UTI confirmed by urinalysis showing bacteria, initiate empiric treatment with nitrofurantoin (100 mg twice daily for 5 days), trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days), or fosfomycin (3 g single dose) as first-line therapy, with the specific choice dependent on your local antibiogram and resistance patterns. 1, 2
First-Line Antibiotic Selection
The choice among the three first-line agents should follow this hierarchy:
- Nitrofurantoin 100 mg twice daily for 5 days is preferred due to minimal resistance rates and low collateral damage to normal flora 1, 2
- Fosfomycin 3 g as a single dose offers convenient single-dose administration but has slightly lower efficacy than other first-line agents 2
- Trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days should only be used if local resistance rates are <20% or if the infecting organism is known to be susceptible 1, 2, 3
Critical Pre-Treatment Considerations
Obtain urine culture and sensitivity testing before initiating antibiotics to allow for culture-directed therapy adjustment if the patient fails to respond 1. However, treatment should not be delayed while awaiting culture results in symptomatic patients 1.
Distinguish Uncomplicated from Complicated UTI
This distinction fundamentally changes management:
Uncomplicated UTI (treat with first-line agents for 3-7 days):
- Otherwise healthy, non-pregnant women 1, 2
- No structural/functional urinary tract abnormalities 1
- No recent instrumentation 1
Complicated UTI (requires broader coverage and longer duration):
- Males with UTI 1
- Pregnancy 1
- Diabetes mellitus 1
- Immunosuppression 1
- Obstruction, foreign body, incomplete voiding, or vesicoureteral reflux 1
- Recent instrumentation 1
- Healthcare-associated infections 1
- ESBL-producing or multidrug-resistant organisms 1
Treatment Duration
Treat for the shortest effective duration to minimize resistance development:
- Uncomplicated cystitis: 3-7 days maximum depending on agent selected 1
- Complicated UTI: 7 days for most cases 1
- Complicated UTI in males: 14 days when prostatitis cannot be excluded 1
Second-Line Options
Use second-line agents only when first-line options are contraindicated or based on resistance patterns:
- Fluoroquinolones (ciprofloxacin, levofloxacin): Only if local resistance <10% and patient has not used fluoroquinolones in the last 6 months 1, 2
- Beta-lactams (amoxicillin-clavulanate, cephalexin): Consider for patients with allergies to first-line agents 2, 4
Important caveat: Fluoroquinolones should be restricted due to increasing resistance rates and should not be used empirically in urology patients 1, 5, 6.
Management of Complicated UTI with Systemic Symptoms
For patients with fever, flank pain, or systemic symptoms suggesting pyelonephritis or complicated infection:
Empiric parenteral therapy options 1:
- Amoxicillin plus aminoglycoside
- Second-generation cephalosporin plus aminoglycoside
- Intravenous third-generation cephalosporin
Transition to oral therapy once hemodynamically stable and afebrile for ≥48 hours 1.
Critical Pitfalls to Avoid
- Do not treat asymptomatic bacteriuria except in pregnant women or before invasive urologic procedures, as treatment increases antimicrobial resistance without benefit 1, 2
- Do not use fluoroquinolones empirically given high resistance rates in many communities 1, 5
- Do not routinely obtain imaging or cystoscopy for index presentation of recurrent UTI 1
- Avoid broad-spectrum antibiotics when narrow-spectrum agents are effective to minimize collateral damage and resistance 1
Antimicrobial Stewardship Principles
Tailor therapy based on culture results once available, narrowing coverage to the most specific effective agent 1. Knowledge of local resistance patterns (your institution's antibiogram) is essential for appropriate empiric selection 1.