What is the best treatment approach for a patient with a complicated urinary tract infection due to ESBL-producing E. coli and Candida albicans, with an indwelling catheter?

Treatment of ESBL-Producing E. coli and Candida Albicans CAUTI

This patient requires immediate catheter replacement (if in place ≥2 weeks), followed by targeted antimicrobial therapy with a carbapenem (meropenem, imipenem, or ertapenem) for the ESBL E. coli, plus fluconazole for the Candida albicans, with treatment duration of 7-14 days depending on clinical response. 1, 2

Critical First Steps: Catheter Management

Replace the indwelling catheter immediately if it has been in place for ≥2 weeks before initiating antimicrobial therapy. 1, 2 This intervention:

• Hastens symptom resolution 1
• Reduces risk of subsequent infection 1
• Removes the biofilm that protects organisms from antimicrobials 3

The biofilm on old catheters may not accurately reflect the bladder infection status, so obtain a urine culture from the freshly placed catheter before starting antibiotics. 2

Antibiotic Selection for ESBL E. coli

Optimal Choices Based on Susceptibility

Your culture shows the ESBL E. coli is susceptible to multiple agents, but carbapenems remain the gold standard for serious ESBL infections:

• Meropenem (≤0.5, S) - Preferred option 1
• Imipenem (≤0.25, S) - Equally effective 1
• Ertapenem (≤0.25, S) - Once-daily dosing advantage 1

Alternative Agents (If Carbapenem-Sparing Desired)

While the organism shows susceptibility to several non-carbapenem options, these should be considered carefully:

• Piperacillin/tazobactam (≤2/4, S) - Acceptable alternative for less severe infections 1
• Ceftolozane/tazobactam (≤1/4, S) - Newer option with excellent activity 1
• Amoxicillin/clavulanic acid (8/4, S) - Could be used for step-down oral therapy after clinical improvement, but NOT as first-line empiric therapy for CAUTI 1

Important caveat: The European Association of Urology recommends third-generation cephalosporins or aminoglycoside-containing combinations as first-line empiric therapy for complicated UTIs, but your organism is resistant to ceftriaxone and ceftazidime. 1, 2 This underscores why culture-directed therapy is essential for CAUTI. 1

Agents to Avoid

Do NOT use the following despite in vitro susceptibility for this complicated CAUTI:

• Nitrofurantoin - Inadequate tissue penetration for complicated UTI 4
• Gentamicin/tobramycin/amikacin alone - Should not be used as monotherapy for established infection 1, 2

Antifungal Therapy for Candida Albicans

Fluconazole is the antifungal agent of choice for Candida UTI, achieving high urine concentrations with oral formulation. 5

When to Treat the Candida

This is a critical decision point. The presence of >100,000 CFU/mL Candida with an indwelling catheter requires careful assessment:

• If the patient is symptomatic (fever, systemic signs): Treat with fluconazole 200-400 mg daily 5
• If asymptomatic: Consider catheter removal/replacement alone first, as this clears candiduria in almost 40-50% of patients 1, 5

However, given the concurrent bacterial CAUTI requiring treatment, it is reasonable to treat both organisms simultaneously to avoid the risk of fungal progression during antibacterial therapy. 5

Fluconazole Dosing

• Loading dose: 400 mg on day 1
• Maintenance: 200-400 mg daily 5
• Duration: 7-14 days depending on clinical response 5

Do NOT use echinocandins or newer azoles for urinary Candida - they fail to achieve adequate urine concentrations. 5

Treatment Duration

The Infectious Diseases Society of America provides clear guidance:

• 7 days if symptoms resolve promptly 1, 2
• 10-14 days for delayed response 1, 2
• 14 days recommended for males when prostatitis cannot be excluded 2

Given the polymicrobial nature (ESBL E. coli + Candida + mixed flora), err toward 10-14 days of therapy. 1, 2

The Polymicrobial Flora Issue

Your culture shows "multiple gram positive and negative organisms" at 10,000-30,000 CFU/mL. Do not treat these lower-count organisms - they represent catheter colonization, not infection. 6 Focus therapy on the two organisms present at >100,000 CFU/mL (ESBL E. coli and Candida albicans). 1, 2

Critical Pitfalls to Avoid

Do not treat asymptomatic bacteriuria in catheterized patients - but this patient's urinalysis shows clear signs of infection (WBC >180/HPF, WBC clumps, 2+ leukocyte esterase, positive nitrites). 6 This is NOT asymptomatic bacteriuria; this requires treatment.

Do not use fluoroquinolones - your organism is resistant to both ciprofloxacin and levofloxacin. 2 Even if susceptible, fluoroquinolones should only be used if local resistance is <10% and the patient hasn't used them in the last 6 months. 2

Do not obtain cultures from the old catheter if replacing - the biofilm will not accurately reflect bladder infection. 2

Definitive Catheter Management

Remove the catheter as soon as clinically appropriate - the duration of catheterization is the most important risk factor for CAUTI development. 1, 2 Every day the catheter remains increases infection risk by 3-5%. 6

If the catheter must remain long-term, understand that antimicrobials will only temporarily suppress bacteriuria, with universal recurrence (often with more resistant organisms). 6

Monitoring and Follow-Up

• Assess clinical response at 48-72 hours 1
• If no improvement, consider imaging to exclude obstruction or abscess 2
• Consider follow-up urine culture after treatment completion to confirm eradication 1
• Monitor for C. difficile infection given broad-spectrum antimicrobial exposure 6