What are the recommended IV (intravenous) antibiotics for E. coli coverage in a urinary tract infection (UTI)?

IV Antibiotics for E. coli UTI Coverage

For uncomplicated E. coli UTIs requiring IV therapy, ceftriaxone 50 mg/kg/dose (max 2g) IV every 24 hours is the preferred first-line agent, with treatment duration of 5-7 days for complicated cases. 1

First-Line IV Options by Clinical Scenario

Uncomplicated UTI (Requiring IV Therapy)

• Ceftriaxone 50 mg/kg/dose IV every 24 hours (maximum 2g per dose) is the standard empiric choice for E. coli coverage 1
• Duration: 5-7 days for complicated UTI 1
• This provides excellent E. coli coverage with once-daily dosing convenience 1

Complicated UTI or Pyelonephritis

For moderate to severe infections:

• Ceftriaxone 50-100 mg/kg/day IV (divided every 12-24 hours, maximum 4g/day) 1
• Alternative: Ceftazidime 150 mg/kg/day IV divided every 8 hours (maximum 6g/day) 1
• Alternative: Gentamicin 5-7 mg/kg IV every 24 hours 1
• Alternative: Amikacin 15 mg/kg IV every 24 hours 1

Pediatric Considerations (8-60 Days Old)

• Ages 29-60 days: Ceftriaxone 50 mg/kg/dose IV every 24 hours 1
• Ages 22-28 days: Ceftriaxone 50 mg/kg/dose IV every 24 hours 1
• Ages 8-21 days: Ampicillin 150 mg/kg/day IV divided every 8 hours PLUS either ceftazidime 150 mg/kg/day IV divided every 8 hours OR gentamicin 4 mg/kg IV every 24 hours 1

Second-Line Options for Resistant or Severe Cases

Extended-Spectrum Cephalosporin-Resistant E. coli (ESCR-E)

When resistance is suspected or confirmed:

• Ertapenem 1g IV every 24 hours (preferred carbapenem for non-severe infections) 1
• Meropenem-vaborbactam 4g IV every 8 hours 1
• Imipenem-cilastatin-relebactam 1.25g IV every 6 hours 1
• Ceftazidime-avibactam 2.5g IV every 8 hours 1

Carbapenem-Resistant Enterobacterales (CRE)

For documented CRE infections:

• Ceftazidime-avibactam 2.5g IV every 8 hours 1
• Meropenem-vaborbactam 4g IV every 8 hours 1
• Plazomicin 15 mg/kg IV every 12 hours 1

Alternative Agents Based on Susceptibility

Fluoroquinolones (When Susceptible)

• Ciprofloxacin 400 mg IV every 12 hours (pediatric: 6-10 mg/kg IV every 8 hours, max 400 mg/dose) 2
• Levofloxacin IV (alternative option) 1
• Note: High resistance rates in many communities limit empiric use 3

Beta-Lactam/Beta-Lactamase Inhibitors

• Piperacillin-tazobactam 3.375-4.5g IV every 6-8 hours 1, 3
• Ampicillin-sulbactam (for susceptible strains) 1
• These provide broader coverage but should be reserved based on susceptibility 1

Critical Prescribing Considerations

Aminoglycoside Use

• Single daily dosing is preferred for both efficacy and reduced nephrotoxicity 1
• Avoid in combination with other nephrotoxic drugs or renal dysfunction 1
• Consider for simple cystitis due to CRE as single-dose therapy 1
• Gentamicin provides synergy with ampicillin against enterococci 1

Carbapenem Stewardship

• Reserve carbapenems for severe infections or documented resistance to preserve their efficacy 1
• Ertapenem is preferred over meropenem/imipenem for non-severe infections to preserve broader-spectrum agents 1
• Single administration of ertapenem makes it practical for outpatient parenteral therapy 1

Duration of Therapy

• Uncomplicated UTI: 5-7 days 1
• Complicated UTI/pyelonephritis: 7-14 days 1
• Bacteremia: 10-14 days 1
• Adjust based on clinical response and source control 1

Common Pitfalls to Avoid

Empiric Selection Errors

• Do not use ampicillin alone empirically - E. coli resistance rates are too high (>40% in many areas) 4, 3
• Avoid fluoroquinolones if recent exposure or in areas with >10% resistance 3
• Do not use trimethoprim-sulfamethoxazole empirically without susceptibility data due to high resistance rates 3, 5

Dosing Mistakes

• Ceftriaxone maximum is 2g per dose for UTI (4g/day for meningitis) 1
• Gentamicin dosing is weight-based: 5-7 mg/kg/day, not fixed dosing 1
• Adjust all doses for renal impairment except ceftriaxone (which has dual elimination) 2, 6

Inappropriate Narrowing

• Obtain cultures before starting therapy whenever possible 4
• De-escalate based on susceptibilities within 48-72 hours 1
• Switch to oral therapy when clinically stable and susceptibilities allow 1, 3

Special Population Errors

• Neonates <21 days require ampicillin coverage for Listeria and Group B Streptococcus in addition to Gram-negative coverage 1
• Do not use ceftriaxone in neonates with hyperbilirubinemia due to displacement from albumin 1
• Avoid nitrofurantoin for pyelonephritis - inadequate tissue penetration despite excellent urine levels 3