What is the appropriate treatment for a patient with a severe urinary tract infection caused by ESBL-producing Escherichia coli and Candida albicans, with an indwelling catheter in place?

Treatment of Catheter-Associated UTI with ESBL E. coli and Candida albicans

For this patient with symptomatic catheter-associated UTI caused by ESBL-producing E. coli and Candida albicans, remove the indwelling catheter immediately and initiate systemic therapy with a carbapenem (meropenem, imipenem, or ertapenem) for the bacterial infection plus an echinocandin (caspofungin, micafungin, or anidulafungin) or fluconazole 400 mg daily for the candidemia, treating for 7-14 days. 1

Immediate Catheter Management

• The indwelling catheter must be removed immediately given the presence of both ESBL-producing bacteria and Candida albicans at >100,000 CFU/mL 1
• Catheter retention with Candida infection is associated with increased mortality, prolonged candidemia, and treatment failure 1
• For ESBL-producing organisms with biofilm formation on catheters, removal is essential as antimicrobial therapy alone cannot eradicate the biofilm 1, 2
• If catheter removal is temporarily impossible due to lack of venous access alternatives, close clinical monitoring with blood cultures is mandatory, though this significantly increases treatment failure risk 1

Antimicrobial Selection for ESBL E. coli

Carbapenems are the definitive treatment for severe ESBL-producing E. coli infections 3, 4

• Based on susceptibility results, appropriate options include:

  • Meropenem ≤0.5 MIC (Susceptible) 3
  • Imipenem ≤0.25 MIC (Susceptible) 3
  • Ertapenem ≤0.25 MIC (Susceptible) 3

• Alternative agents showing susceptibility in this case include:

  • Piperacillin-tazobactam (≤2/4 MIC) - though carbapenems are preferred for severe infections 3
  • Aminoglycosides: gentamicin, tobramycin, or amikacin 3
  • Ceftolozane-tazobactam (≤1/4 MIC) 3

Critical caveat: Despite in vitro susceptibility to cephalosporins or piperacillin-tazobactam, ESBL-producing organisms treated with these agents show poor clinical outcomes compared to carbapenems, even when appearing susceptible on testing 1, 4

Antifungal Treatment for Candida albicans

All cases of catheter-associated candiduria with >100,000 CFU/mL require systemic antifungal therapy, not just catheter removal 1, 5

First-line options:

• Fluconazole 400 mg daily for 14 days after first negative blood culture (preferred for C. albicans) 1, 5

• Echinocandins (if azole resistance suspected or patient critically ill):

  • Caspofungin: 70 mg IV loading dose, then 50 mg daily 1
  • Micafungin: 100 mg IV daily 1
  • Anidulafungin: 200 mg IV loading dose, then 100 mg daily 1

• Lipid formulations of amphotericin B (3-5 mg/kg daily) are highly effective but reserved for refractory cases due to toxicity 1

Important distinction: This is NOT asymptomatic bacteriuria—the patient has significant pyuria (>180 WBC/HPF), positive leukocyte esterase, nitrites, and bacterial clumps indicating true infection requiring treatment 1, 6

Duration of Therapy

• 7-14 days of systemic antibiotics for the ESBL E. coli after catheter removal 1, 3
• 14 days of antifungal therapy measured from the first negative blood culture for Candida 1, 5
• Shorter 7-day courses may be considered only if the patient responds promptly and completely 1, 2

Monitoring and Follow-up

• Obtain blood cultures to rule out candidemia given the high colony count and presence of an indwelling catheter 1
• Repeat urine culture 48 hours after catheter removal to document clearance 1
• Monitor for clinical improvement within 48-72 hours; lack of improvement warrants reassessment and possible imaging for complications 1
• If blood cultures are positive for Candida, evaluate for endocarditis and metastatic foci of infection 1

Common Pitfalls to Avoid

• Do not treat this as asymptomatic bacteriuria—the presence of symptoms (turbid urine, pyuria, positive nitrites, leukocyte esterase) indicates true infection 1, 6
• Do not use cephalosporins or fluoroquinolones despite apparent susceptibility on testing, as ESBL organisms show treatment failure with these agents 1, 3
• Do not attempt catheter salvage with antibiotic lock therapy when Candida is present, as this approach has unacceptably high failure rates and mortality 1
• Do not use echinocandins or newer azoles for urinary candidiasis if oral therapy is appropriate, as they achieve inadequate urine concentrations 5
• Do not delay catheter removal hoping antibiotics alone will clear the infection—biofilm formation prevents antimicrobial penetration 1, 2