What alternative antibiotic treatment is recommended for E. coli urinary tract infection not responding to Keflex (Cephalexin)?

Switch to Ceftriaxone (Rocephin) Immediately

Based on your culture showing E. coli sensitive to ceftriaxone and cefepime but resistant to cephalexin (intermittent resistance to cefazolin), you should switch to ceftriaxone 1-2g IV/IM daily or cefepime 1-2g IV every 12 hours. 1, 2

Recommended Treatment Based on Infection Severity

For Uncomplicated UTI/Cystitis

• Switch to oral nitrofurantoin 100mg twice daily for 5-7 days if the organism is sensitive and infection is limited to bladder 1, 3
• Alternative: Trimethoprim-sulfamethoxazole 160/800mg twice daily for 3 days only if local resistance <20% and organism is sensitive 1, 3
• Fosfomycin 3g single dose is another option but may have slightly inferior efficacy 3

For Complicated UTI or Pyelonephritis

• Ceftriaxone 1-2g IV/IM once daily for 10-14 days is the preferred choice given your culture sensitivities 1, 2
• Cefepime 1-2g IV every 12 hours for 10 days is equally appropriate for severe infections 2
• For severe infections with septic shock, carbapenems (meropenem or imipenem) are recommended, though ertapenem may be used without septic shock 1

Critical Decision Points

Why Keflex Failed

• Your E. coli shows intermittent resistance to cefazolin (same class as cephalexin), explaining treatment failure 4
• First-generation cephalosporins like cephalexin have increasing resistance rates in E. coli UTIs 4
• Never continue cephalexin when culture shows cefazolin resistance 1

Antibiotics to AVOID

• Do NOT use ciprofloxacin or levofloxacin - your culture shows fluoroquinolone resistance 1, 3
• Do NOT use ampicillin or amoxicillin - E. coli has 75% median resistance rates globally 1
• Avoid aminoglycosides as monotherapy for anything beyond short-course UTI treatment 1

Treatment Duration Algorithm

For lower UTI (cystitis):

• Nitrofurantoin: 5-7 days 3
• Trimethoprim-sulfamethoxazole: 3 days 3
• Fosfomycin: Single dose 3

For pyelonephritis:

• Ceftriaxone or cefepime: 10-14 days 1, 2
• Fluoroquinolones (if sensitive): 5-7 days 3

For men (when prostatitis cannot be excluded):

• Extend treatment to 14 days minimum 3

Antibiotic Stewardship Considerations

• Reserve carbapenems for severe infections or extended-spectrum beta-lactamase (ESBL) producers 1
• Ceftriaxone and cefepime are appropriate for your 3rd-generation cephalosporin-sensitive E. coli without overusing carbapenems 1
• Once clinically stable, consider step-down to oral therapy based on repeat culture sensitivities 1

Common Pitfalls

• Do not empirically use fluoroquinolones if patient used them in last 6 months - resistance risk is high 3
• Do not use cefepime or cefoxitin for ESBL-producing organisms - insufficient evidence for efficacy 1
• Verify renal function before dosing - cefepime requires dose adjustment for creatinine clearance <60 mL/min 2