Treatment Protocol for Fluconazole-Resistant Candida glabrata
For adults with fluconazole-resistant Candida glabrata infection, initiate an echinocandin (caspofungin 70 mg loading dose then 50 mg daily, micafungin 100 mg daily, or anidulafungin 200 mg loading dose then 100 mg daily) as first-line therapy. 1
Initial Therapy Selection
The Infectious Diseases Society of America (IDSA) provides clear guidance that echinocandins are the preferred initial treatment for C. glabrata infections, particularly when fluconazole resistance is suspected or confirmed 1:
- Caspofungin: 70 mg loading dose, then 50 mg daily 1
- Micafungin: 100 mg daily 1
- Anidulafungin: 200 mg loading dose, then 100 mg daily 1
Why Echinocandins First?
C. glabrata has intrinsically reduced susceptibility to fluconazole, with resistance mediated by upregulation of CDR genes encoding drug efflux pumps 2. Many isolates are intermediately susceptible or resistant to fluconazole 2. Prior fluconazole exposure significantly increases the risk of infection with less-susceptible isolates (OR 12.24) 3.
Susceptibility Testing Requirements
Obtain azole susceptibility testing on all C. glabrata bloodstream and clinically relevant isolates 1. Additionally, consider echinocandin susceptibility testing in patients who have had prior echinocandin treatment 1.
This testing is critical because:
- It guides potential step-down therapy decisions
- C. glabrata resistance patterns vary significantly
- Cross-resistance between azoles can occur 4
Step-Down Therapy Considerations
Transition to oral fluconazole is only appropriate if the isolate tests susceptible to fluconazole AND the patient is clinically stable with negative repeat blood cultures 1.
Specific Criteria for Step-Down:
If susceptibility testing confirms fluconazole susceptibility, consider transition after 5-7 days to 1:
- High-dose fluconazole: 800 mg (12 mg/kg) daily, OR
- Voriconazole: 200-300 mg (3-4 mg/kg) twice daily (if voriconazole-susceptible)
Recent evidence supports fluconazole step-down as safe and reasonable when appropriately selected 5. A dose:MIC ratio >12.5 is associated with significantly higher response rates when fluconazole is used (49% vs 20% for ratios ≤12.5) 6.
Alternative Agents
Lipid Formulation Amphotericin B
Use lipid formulation amphotericin B (3-5 mg/kg daily) if there is intolerance, limited availability, or resistance to echinocandins 1.
This is particularly important for:
- Suspected azole- and echinocandin-resistant infections 1
- Patients who cannot tolerate echinocandins 1
Site-Specific Considerations
For urinary tract infections with fluconazole-resistant C. glabrata 1:
- Cystitis: Amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days OR oral flucytosine 25 mg/kg four times daily for 7-10 days 1
- Pyelonephritis: Amphotericin B deoxycholate 0.3-0.6 mg/kg daily for 1-7 days with or without flucytosine 25 mg/kg four times daily 1
- Remove indwelling bladder catheters whenever feasible 1
Duration of Therapy
Continue treatment for 2 weeks after documented clearance of Candida from the bloodstream and resolution of symptoms 1.
Key monitoring requirements 1:
- Perform follow-up blood cultures daily or every other day to establish clearance
- Obtain dilated ophthalmological examination within the first week after diagnosis
- Remove central venous catheters when feasible and safe 1
Critical Pitfalls to Avoid
Never use standard-dose fluconazole (400 mg daily) for C. glabrata - if fluconazole is used at all, it must be high-dose (800 mg daily) and only for susceptible isolates 1
Do not assume fluconazole susceptibility - C. glabrata resistance is common, with over 90% of some populations showing reduced susceptibility 2, 3
Avoid empiric fluconazole in high-risk patients - those with prior azole exposure, diabetes, or central venous catheters are at significantly higher risk for resistant isolates 3
Do not prematurely discontinue therapy - inadequate treatment duration leads to relapse 1
Consider cross-resistance - mutations in transcription factors (PDR1) that confer fluconazole resistance may also confer reduced susceptibility to newer agents 4
Emerging Resistance Concerns
C. glabrata develops resistance through multiple mechanisms 2:
- Upregulation of CDR genes (ATP-binding cassette transporters)
- Point mutations in ERG11 (target enzyme)
- Overexpression of efflux pumps
High concentrations of fluconazole can induce simultaneous development of both tolerance and resistance in C. glabrata 7, making echinocandins the safer initial choice.