What is the treatment for an Escherichia coli (E. coli) urinary tract infection (UTI)?

Treatment for E. coli Urinary Tract Infection

For uncomplicated E. coli UTIs in non-pregnant women, use nitrofurantoin for 5 days, fosfomycin 3g single dose, or trimethoprim-sulfamethoxazole for 3 days (only if local resistance is <20% and no recent use in past 3-6 months) as first-line therapy. 1, 2

First-Line Treatment Selection Algorithm

For Uncomplicated Cystitis (Non-Pregnant Women):

Preferred options:

• Nitrofurantoin: 100mg twice daily for 5 days 1, 2
• Fosfomycin tromethamine: 3g single oral dose 1, 2
• Trimethoprim-sulfamethoxazole (TMP-SMX): 160/800mg twice daily for 3 days—only if local E. coli resistance is <20% AND patient has not used this antibiotic in the previous 3-6 months 1, 3

Critical decision point: Check local antibiogram resistance patterns before prescribing empiric therapy, as this significantly impacts treatment success 1, 2. If local TMP-SMX resistance exceeds 20%, or if the patient has recent exposure to this antibiotic, avoid it entirely due to increased resistance risk 4, 1.

Avoid fluoroquinolones as first-line therapy due to increasing resistance rates, collateral damage to protective microbiota, and FDA warnings about disabling adverse effects that create an unfavorable risk-benefit ratio for uncomplicated UTIs 4, 1, 2, 5.

For Acute Pyelonephritis (Outpatient):

If local fluoroquinolone resistance is <10%:

• Ciprofloxacin 500mg twice daily for 7 days 1, 2

If using TMP-SMX (only with confirmed susceptibility):

• TMP-SMX 160/800mg twice daily for 14 days 1, 2

If using oral β-lactams:

• Start with an initial IV dose of ceftriaxone 1g or an aminoglycoside, then transition to oral therapy 1, 2

The longer duration for pyelonephritis (7-14 days) is essential—inadequate treatment duration is a common pitfall that increases recurrence risk 1, 2.

For Hospitalized Patients with Pyelonephritis:

Initial IV therapy options:

• Fluoroquinolone (if susceptible) 1
• Aminoglycoside with or without ampicillin 1
• Extended-spectrum cephalosporin or penicillin 1
• Carbapenem 1

Tailor therapy based on culture and susceptibility results within 48-72 hours 1. Treatment duration should be 7-14 days depending on clinical response and antibiotic choice 1, 2.

Pediatric UTI Treatment (Ages 2-24 Months)

For febrile infants with confirmed UTI:

Oral options:

• Cefixime 8mg/kg per day in 1 dose 1

Parenteral options (if unable to retain oral fluids):

• Ceftriaxone 75mg/kg every 24 hours 4, 1
• Cefotaxime 150mg/kg per day divided every 6-8 hours 4, 1
• Gentamicin 7.5mg/kg per day divided every 8 hours 4, 1

Treatment duration: 7-14 days 4, 1. Adjust antimicrobial therapy according to sensitivities once culture results are available 4. Obtain renal and bladder ultrasonography after UTI is confirmed to detect anatomic abnormalities 4, 1.

Multidrug-Resistant and Complicated E. coli UTIs

For Extended-Spectrum β-Lactamase (ESBL)-Producing E. coli:

Oral options for uncomplicated UTI:

• Nitrofurantoin 6
• Fosfomycin 6
• Amoxicillin-clavulanate (for ESBL E. coli only, not Klebsiella) 6

Parenteral options for complicated UTI/pyelonephritis:

• Piperacillin-tazobactam (for ESBL E. coli only) 4, 6
• Carbapenems (meropenem, ertapenem) 4, 6
• Ceftazidime-avibactam 6
• Aminoglycosides (consider nephrotoxicity risk after 7 days) 4, 6

The European Society of Clinical Microbiology and Infectious Diseases found moderate-certainty evidence that β-lactam/β-lactamase inhibitor combinations are non-inferior to carbapenems for pyelonephritis caused by third-generation cephalosporin-resistant E. coli 4.

For Carbapenem-Resistant E. coli (CRE):

Preferred options:

• Ceftazidime-avibactam 2.5g IV every 8 hours 1, 6
• Meropenem-vaborbactam 4g IV every 8 hours 1, 6
• Imipenem-cilastatin-relebactam 1.25g IV every 6 hours 1, 6

For simple cystitis due to CRE:

• Single-dose aminoglycoside may be considered 1

These newer β-lactam/β-lactamase inhibitor combinations represent high-certainty evidence for carbapenem-sparing treatment of resistant organisms 4, 1.

Recurrent UTI Management

Obtain pre-treatment urine culture when acute UTI is suspected in patients with recurrent UTIs—failing to do this is a critical pitfall 4, 1, 2. Use prior culture data to guide empiric therapy while awaiting results 4.

Do NOT treat asymptomatic bacteriuria in women with recurrent UTIs, as this fosters antimicrobial resistance and increases the number of symptomatic recurrence episodes 4, 2.

Prevention Strategies for Recurrent UTI:

For premenopausal women with UTIs related to sexual activity:

• Post-coital antibiotics (single dose of TMP-SMX, nitrofurantoin, or cephalexin) 4, 1, 2

For premenopausal women with infections unrelated to sexual activity:

• Low-dose daily antibiotic prophylaxis (nitrofurantoin 50-100mg daily or TMP-SMX 40/200mg daily) for 6-12 months 4

For postmenopausal women:

• Vaginal estrogen with or without lactobacillus-containing probiotics 4
• Methenamine hippurate 1g twice daily as a nonantibiotic alternative 4

Nonantibiotic alternatives with some evidence:

• Oral immunostimulant OM-89 (decreased recurrent UTI with RR 0.61) 4
• Cranberry products 100-500mg daily (modest benefit) 4

The American Urological Association emphasizes that nitrofurantoin resistance decays rapidly (only 5.7% at 9 months vs 20.2% at 3 months), making it an excellent choice for re-treatment 4.

Common Pitfalls to Avoid

• Using fluoroquinolones as first-line therapy for uncomplicated UTIs—reserve as second-line only 4, 1, 2
• Prescribing antibiotics with >20% local resistance rates for empiric therapy 1, 2
• Inadequate treatment duration for pyelonephritis (must be 7-14 days) 1, 2
• Treating asymptomatic bacteriuria in recurrent UTI patients 4, 2
• Failing to obtain urine culture before treatment in recurrent or complicated UTIs 4, 1, 2
• Classifying recurrent UTI as "complicated" without structural/functional abnormalities or immunosuppression, which leads to unnecessary broad-spectrum antibiotic use 4