What is the recommended treatment for a patient with Candida krusei in their urine?

Treatment of Candida krusei in Urine

For symptomatic Candida krusei urinary tract infection, amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days (for cystitis) or 2 weeks (for pyelonephritis) is the recommended first-line treatment, as fluconazole is ineffective due to intrinsic resistance. 1, 2, 3

Critical First Step: Determine if Treatment is Needed

• Treatment is NOT indicated for asymptomatic candiduria in most patients, as candiduria often represents colonization rather than true infection 1, 2, 4

• Treatment IS required for the following high-risk groups even if asymptomatic: 1, 2, 4

  • Neutropenic patients
  • Very low birth-weight infants
  • Patients undergoing urologic procedures or manipulation

• Treatment IS required for symptomatic patients with signs of cystitis (dysuria, frequency, urgency, suprapubic pain) or pyelonephritis (fever, flank pain, systemic symptoms) 1, 2

Essential Source Control Measures (Must Be Done First)

• Remove indwelling urinary catheter immediately if present, as this is critical for treatment success 1, 2

• Eliminate any urinary tract obstruction through surgical or endoscopic intervention, as antifungal therapy alone will fail without addressing obstruction 1, 2

Antifungal Treatment Algorithm

First-Line: Amphotericin B Deoxycholate

• Amphotericin B deoxycholate 0.3-0.6 mg/kg IV daily is the treatment of choice for C. krusei UTI 1, 2

• Duration: 1-7 days for uncomplicated cystitis; 2 weeks for pyelonephritis 1, 2

• This agent achieves adequate urinary concentrations and maintains activity against most C. krusei isolates, though some isolates show resistance 1

Alternative: Amphotericin B Bladder Irrigation (Cystitis Only)

• AmB deoxycholate 50 mg/L in sterile water instilled daily for 5 days can be used for cystitis localized to the bladder 1, 2

• This approach resolves candiduria in 80-90% of patients but has high recurrence rates within weeks 1

• Only appropriate for bladder infections, not pyelonephritis or systemic involvement 1

• Generally discouraged except when systemic therapy cannot be used 1

Why Standard Agents Don't Work for C. krusei

Fluconazole: Completely Ineffective

• C. krusei has intrinsic resistance to fluconazole and should always be considered resistant 1, 3

• The FDA drug label explicitly states "Candida krusei should be considered to be resistant to fluconazole" 3

• This resistance is mediated by reduced sensitivity of the target enzyme to azole inhibition 3

Flucytosine: Poor Activity

• Flucytosine demonstrates poor activity against C. krusei specifically 1

• Additional limitations include toxicity and rapid resistance development when used as monotherapy 1

Echinocandins: Limited Role

• Echinocandins achieve minimal urinary concentrations and are generally ineffective for UTI 1, 5

• However, echinocandins CAN be effective for kidney infections from hematogenous spread (candidemia with renal involvement) because adequate tissue concentrations are achieved despite poor urine levels 1, 6

• Case reports show both success and failure when used for fluconazole-resistant UTI 1, 7

• One case report documented successful eradication of chronic symptomatic C. krusei UTI with micafungin 150 mg daily in a transplant recipient, though this is not standard therapy 7

Other Azoles and Lipid Amphotericin Formulations

• Voriconazole and other azoles achieve minimal urinary excretion and should not be used for UTI 1, 5

• Lipid formulations of amphotericin B do NOT achieve adequate urine concentrations and should not be used for UTI 1

Special Situations Requiring Surgical Intervention

Fungus Balls (Bezoars)

• Surgical or endoscopic removal is central to successful treatment in adults with obstructing fungal masses 1

• Antifungal therapy alone is insufficient without mechanical removal 1

• Irrigation through nephrostomy tubes with AmB deoxycholate 25-50 mg in 200-500 mL sterile water can be used as adjunctive therapy 1

Complicated Infections

• Abscesses, emphysematous pyelonephritis, or extensive tissue involvement require surgical debridement in addition to antifungal therapy 1, 6

Monitoring and Follow-Up

• Obtain repeat urine cultures to document clearance of infection 2

• Continue treatment for full duration even if symptoms improve earlier 1, 2

• Monitor for recurrence, especially if risk factors (catheter, obstruction) persist 1

Critical Pitfall to Avoid

The most common error is attempting to treat C. krusei UTI with fluconazole based on standard Candida UTI protocols—this will fail due to intrinsic resistance and delays appropriate therapy 1, 3, 4. Always verify species identification and use amphotericin B deoxycholate for C. krusei.