What is the best antibiotic for an inpatient with a urinary tract infection (UTI)?

Best Antibiotic for Inpatient UTI

For hospitalized patients with uncomplicated pyelonephritis requiring intravenous therapy, initiate treatment with a fluoroquinolone (ciprofloxacin 400 mg IV twice daily or levofloxacin 750 mg IV daily), an extended-spectrum cephalosporin (ceftriaxone 1-2 g IV daily), or piperacillin-tazobactam (2.5-4.5 g IV three times daily), with the choice guided by local resistance patterns. 1

Initial Empiric Therapy Selection

The selection of empiric antibiotic therapy for inpatient UTI depends critically on whether the infection is uncomplicated pyelonephritis versus complicated UTI, and on local antimicrobial resistance patterns:

For Uncomplicated Pyelonephritis Requiring Hospitalization

• First-line parenteral options include fluoroquinolones (ciprofloxacin 400 mg IV twice daily or levofloxacin 750 mg IV daily), extended-spectrum cephalosporins (ceftriaxone 1-2 g IV daily or cefotaxime 2 g IV three times daily), or piperacillin-tazobactam (2.5-4.5 g IV three times daily) 1

• Aminoglycosides (gentamicin 5 mg/kg IV daily or amikacin 15 mg/kg IV daily) with or without ampicillin are also effective options, though not studied as monotherapy 1

• Fluoroquinolones should only be used if local resistance rates are less than 10% 1

For Complicated UTI

• The microbial spectrum is broader than uncomplicated UTI, with higher rates of antimicrobial resistance including E. coli, Proteus spp., Klebsiella spp., Pseudomonas spp., Serratia spp., and Enterococcus spp. 1

• Empiric therapy must be tailored to local resistance patterns and the patient's risk factors for multidrug-resistant organisms 1

• Piperacillin-tazobactam demonstrates excellent efficacy with 86% clinical cure rates and 82% pathogen eradication in complicated UTI 2, 3

When to Reserve Carbapenems and Novel Agents

• Carbapenems (imipenem/cilastatin 0.5 g IV three times daily or meropenem 1 g IV three times daily) and novel broad-spectrum agents should be reserved for patients with early culture results indicating multidrug-resistant organisms 1

• For third-generation cephalosporin-resistant Enterobacterales with severe infection, carbapenems (imipenem or meropenem) are strongly recommended 1

• Novel agents like ceftolozane-tazobactam, ceftazidime-avibactam, cefiderocol, and meropenem-vaborbactam should be reserved for extensively resistant bacteria due to antimicrobial stewardship considerations 1

Critical Decision Points

Assess Severity and Complicating Factors

• Identify if the patient has septic shock, as this mandates more aggressive empiric coverage 1

• Evaluate for complicating factors including obstruction, foreign bodies, incomplete voiding, vesicoureteral reflux, recent instrumentation, immunosuppression, or healthcare-associated infection 1

• Male gender, pregnancy, and diabetes mellitus are also considered complicating factors 1

Obtain Cultures Before Initiating Therapy

• Always obtain urine culture and sensitivity testing before starting antibiotics in hospitalized patients 1

• Blood cultures should be obtained if bacteremia is suspected 1

Consider Local Resistance Patterns

• The choice between empiric agents must be based on local antibiograms 1, 4, 5

• High rates of resistance to trimethoprim-sulfamethoxazole and ciprofloxacin in many communities preclude their empiric use 5

Transition to Oral Therapy

• Once the patient is clinically stable and able to tolerate oral medications, transition to oral therapy based on culture sensitivities 1

• Oral step-down options include ciprofloxacin 500-750 mg twice daily for 7 days, levofloxacin 750 mg daily for 5 days, or trimethoprim-sulfamethoxazole 160/800 mg twice daily for 14 days (if susceptible) 1

Treatment Duration

• Treat for as short a duration as reasonable, generally no longer than 7 days for most cases 1

• Longer courses (up to 14 days) may be required for patients with positive blood cultures at baseline 6

Common Pitfalls to Avoid

• Do not use fluoroquinolones empirically if local resistance exceeds 10% 1

• Avoid using carbapenems or novel broad-spectrum agents empirically unless multidrug-resistant organisms are documented or strongly suspected, as this promotes further resistance 1

• Do not treat asymptomatic bacteriuria in non-pregnant patients, as this increases antibiotic resistance without clinical benefit 1

• Imipenem-cilastatin is not indicated for CNS infections and should not be used in patients with meningitis 7

• Avoid unnecessarily prolonged courses of antibiotics, as this promotes resistance and disrupts protective microbiota 1

Special Considerations for Multidrug-Resistant Organisms

For ESBL-Producing Enterobacterales

• Carbapenems remain the treatment of choice for severe infections 1

• For non-severe complicated UTI, consider alternatives like aminoglycosides (including plazomicin), fosfomycin, or piperacillin-tazobactam based on susceptibilities 1, 4, 5

For Carbapenem-Resistant Enterobacterales

• Treatment options include ceftazidime-avibactam, meropenem-vaborbactam, cefiderocol, colistin, fosfomycin, or aminoglycosides 1, 5

For Multidrug-Resistant Pseudomonas

• Options include ceftolozane-tazobactam, ceftazidime-avibactam, cefiderocol, aminoglycosides, or colistin based on susceptibilities 1, 5