How to treat Candida krusei (a type of fungal infection) in urine?

Treatment of Candida krusei in Urine

For Candida krusei urinary tract infection, amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days is the recommended first-line treatment, as C. krusei exhibits intrinsic resistance to fluconazole. 1

Critical First Step: Distinguish Infection from Colonization

• Treatment is NOT indicated for asymptomatic candiduria unless the patient belongs to high-risk groups: neutropenic patients, very low-birth-weight infants (<1500g), or patients undergoing urologic procedures 1
• For high-risk patients with asymptomatic candiduria, treat as candidemia rather than isolated UTI 1
• Symptomatic patients (dysuria, fever, flank pain, pyuria with clinical correlation) require antifungal therapy 1

Remove Predisposing Factors (Essential)

• Remove indwelling bladder catheter if present - this is a strong recommendation and critical to treatment success 1
• Eliminate any urinary tract obstruction (hydronephrosis, stones, strictures) - strong recommendation 1
• Consider removal or replacement of nephrostomy tubes or stents if feasible 1

Pharmacologic Treatment Algorithm

For Cystitis (Lower UTI):

• Primary option: Amphotericin B deoxycholate 0.3-0.6 mg/kg IV daily for 1-7 days (strong recommendation) 1
• Alternative option: Amphotericin B bladder irrigation 50 mg/L sterile water daily for 5 days (weak recommendation, useful for cystitis specifically) 1
• Duration: Continue for 2 weeks total for cystitis 1

For Pyelonephritis (Upper UTI):

• Amphotericin B deoxycholate 0.3-0.6 mg/kg IV daily for 1-7 days (strong recommendation) 1
• Duration: Continue for 2 weeks and until all symptoms resolve 1

Why Fluconazole Cannot Be Used

• C. krusei exhibits intrinsic resistance to fluconazole - this is a fundamental characteristic of the organism 1, 2
• The FDA drug label explicitly states "Candida krusei should be considered to be resistant to fluconazole" due to reduced sensitivity of the target enzyme 2
• Fluconazole, while the drug of choice for most Candida UTIs, is completely ineffective against C. krusei 1

Important Caveats About Other Antifungals

• Flucytosine is NOT active against C. krusei and should not be used 1
• Lipid formulations of amphotericin B do NOT achieve adequate urine concentrations and should be avoided for UTI 1
• Echinocandins achieve minimal urinary excretion and are generally ineffective for UTI, though there is emerging evidence of success in isolated cases 1, 3
• Other azole agents (voriconazole, posaconazole, isavuconazole) do not achieve adequate urine concentrations for UTI treatment 1

Special Situations

Fungus Balls (Obstructing Masses):

• Surgical or endoscopic removal is strongly recommended - antifungal therapy alone will not resolve obstruction 1
• Add amphotericin B irrigation through nephrostomy tubes if present: 25-50 mg in 200-500 mL sterile water 1
• Antifungal treatment as above should accompany surgical intervention 1

Patients Undergoing Urologic Procedures:

• Treat prophylactically with amphotericin B deoxycholate 0.3-0.6 mg/kg daily for several days before and after the procedure 1

Monitoring

• Obtain repeat urine cultures to document clearance of infection 4
• Monitor for amphotericin B toxicity (nephrotoxicity, electrolyte abnormalities, infusion reactions) 1
• Ensure resolution of symptoms before discontinuing therapy 1

Common Pitfall to Avoid

Do not use fluconazole for C. krusei - this is the most critical error to avoid, as C. krusei is intrinsically resistant and treatment failure is guaranteed 1, 2. The guideline emphasizes that UTIs due to C. krusei "can be extremely difficult to treat" precisely because fluconazole cannot be used 1.