What is a suitable oral (PO) antibiotic choice for a patient with a Klebsiella urinary tract infection (UTI) that is sensitive to cefazolin (Ancef)?

Oral Antibiotic for Cefazolin-Sensitive Klebsiella UTI

Use cephalexin 500 mg PO twice daily for 5-7 days as your first-line oral option for a cefazolin-sensitive Klebsiella UTI. 1

Rationale for Cephalexin

Cephalexin is the most practical oral cephalosporin choice when Klebsiella is sensitive to cefazolin, as cefazolin sensitivity reliably predicts cephalexin susceptibility through CLSI-recommended surrogate testing. 1

• Cephalexin achieves excellent urinary concentrations and demonstrates very good early bacteriological and clinical cure rates in uncomplicated UTIs caused by non-ESBL Enterobacteriaceae including Klebsiella. 1

• Dosing is convenient: 500 mg twice daily (or three times daily for more severe infections), making it a fluoroquinolone-sparing alternative. 1

• Cefazolin-cephalexin surrogate testing as recommended by CLSI and USCAST has recategorized many isolates from resistant to susceptible, expanding the utility of oral first-generation cephalosporins. 1

Alternative Oral Options

If cephalexin is unavailable or not tolerated:

• Cefadroxil 500 mg PO twice daily is equally effective with similar PK/PD properties and comparable bacteriological cure rates. 1

• Cefprozil 500 mg PO once daily demonstrated excellent activity against Klebsiella pneumoniae in clinical trials with comparable efficacy to other oral cephalosporins. 2

Treatment Duration

• 5-7 days is appropriate for uncomplicated lower UTI (cystitis). 1

• 10-14 days should be used if pyelonephritis is suspected or cannot be excluded. 3

Critical Pitfalls to Avoid

• Do not assume all oral cephalosporins are equivalent: First-generation agents (cephalexin, cefadroxil) have superior urinary concentrations compared to second/third-generation oral agents for simple UTI. 1

• Verify the organism is not ESBL-producing: If there is any suspicion of ESBL production (prior ESBL history, recent hospitalization, recent broad-spectrum antibiotic use), cephalexin will fail and you need alternative therapy such as fluoroquinolones or nitrofurantoin pending susceptibilities. 4, 1

• Oral beta-lactams are less effective for pyelonephritis: If treating pyelonephritis with an oral cephalosporin, strongly consider an initial IV dose of ceftriaxone 1 g before transitioning to oral therapy. 3

When Oral Cephalosporins Are Insufficient

If the patient has complicated UTI, pyelonephritis with systemic symptoms, or known/suspected resistance:

• Fluoroquinolones remain first-line for pyelonephritis when local resistance is <10%: ciprofloxacin 500 mg PO twice daily for 7 days or levofloxacin 750 mg PO daily for 5 days. 3

• Trimethoprim-sulfamethoxazole 160/800 mg PO twice daily for 14 days is appropriate if susceptibility is confirmed. 3