Should cefepime and vancomycin be continued in a patient with leukocytosis and a urine culture positive for Proteus mirabilis?

Antibiotic De-escalation Based on Culture Results

You should discontinue vancomycin immediately and narrow cefepime to a more targeted agent based on the Proteus mirabilis susceptibility profile, as the organism is pan-sensitive and there is no evidence of gram-positive infection. 1, 2

Rationale for Discontinuing Vancomycin

• Vancomycin is not indicated as part of standard empirical therapy for febrile neutropenia and should be discontinued within 24-48 hours if no gram-positive infection is identified 1, 3
• Your urine culture shows no gram-positive organisms—only Proteus mirabilis, which is a gram-negative rod 2
• The urinalysis shows no bacteria on microscopy and the culture grew a single organism, making polymicrobial or catheter-related infection unlikely 1
• Continuing vancomycin unnecessarily increases risks of nephrotoxicity, drug-induced neutropenia (which could worsen your patient's existing leukocytosis), and selection of resistant organisms 1, 4

Rationale for De-escalating Cefepime

• Proteus mirabilis is susceptible to multiple narrower-spectrum agents including ampicillin (MIC ≤2), ceftriaxone (MIC ≤1), and ciprofloxacin (MIC ≤0.25) 2
• Guidelines specifically recommend de-escalating to first or second-generation cephalosporins for E. coli, K. pneumoniae, and Proteus mirabilis once susceptibility results are available 1
• Cefepime is appropriate for Proteus mirabilis UTI but represents broader coverage than necessary given the pan-sensitive profile 2, 5

Recommended Antibiotic Adjustment

• Switch from cefepime to ceftriaxone 1-2g IV daily for targeted therapy of pan-sensitive Proteus mirabilis complicated UTI 1, 2
• Alternative options include:
  • Ampicillin 2g IV every 6 hours (organism is ampicillin-susceptible with MIC ≤2) 2
  • Ciprofloxacin 400mg IV every 12 hours (MIC ≤0.25 indicates excellent susceptibility) 1
• Total duration should be 7-10 days for complicated UTI with associated bacteremia (if blood cultures are positive) 1, 2

Clinical Monitoring

• The leukocytosis (WBC 22) may be related to the infection itself rather than requiring continued broad-spectrum coverage 1, 3
• Monitor for clinical improvement (defervescence, resolution of urinary symptoms, decreasing WBC) over the next 48-72 hours 1
• If the patient remains febrile beyond 3-5 days despite targeted therapy, reassess for:
  • Occult abscess or complicated pyelonephritis requiring imaging 1
  • Alternative source of infection 1, 3
  • Drug fever (less likely given documented infection) 1

Key Pitfalls to Avoid

• Do not continue vancomycin "just in case"—this practice increases antimicrobial resistance and adverse effects without improving outcomes in documented gram-negative infections 1, 3
• Do not maintain cefepime indefinitely when narrower agents are appropriate—antimicrobial stewardship principles mandate de-escalation based on culture data 1, 2
• The urinalysis showing 3+ protein and 250 blood suggests possible pyelonephritis or upper tract involvement, but this does not change antibiotic selection—it may extend duration to the full 10 days 1, 2