Treatment of Fluconazole- and Echinocandin-Resistant Candida glabrata
Lipid formulation amphotericin B (3–5 mg/kg daily) is the treatment of choice for suspected or confirmed fluconazole- and echinocandin-resistant Candida glabrata infections.
Primary Recommendation
The 2016 IDSA guidelines explicitly state that among patients with suspected azole- and echinocandin-resistant Candida infections, lipid formulation amphotericin B (3–5 mg/kg daily) is recommended (strong recommendation; low-quality evidence) 1. This represents the only guideline-endorsed option when both major antifungal classes have failed or resistance is documented.
Clinical Context and Rationale
C. glabrata presents unique therapeutic challenges:
- Intrinsic azole resistance: C. glabrata exhibits reduced fluconazole susceptibility, with many isolates categorized as intermediate or resistant 2
- Emerging echinocandin resistance: Recent surveillance data show 3.1–3.6% of U.S. C. glabrata isolates are echinocandin-resistant, primarily due to FKS1 or FKS2 mutations 3
- Multidrug resistance: Approximately 36% of echinocandin-resistant C. glabrata isolates are also fluconazole-resistant 3
Dosing and Administration
Lipid formulation amphotericin B:
- Dose: 3–5 mg/kg daily intravenously
- Formulations: Liposomal amphotericin B preferred over amphotericin B lipid complex due to better tolerability
- Duration: Continue for at least 2 weeks after documented clearance from bloodstream and resolution of symptoms 1
Alternative and Emerging Options
While not guideline-endorsed for dual resistance, consider:
Combination therapy: Case reports suggest potential benefit of echinocandin plus liposomal amphotericin B for multidistrict infections when pharmacokinetic barriers exist 4. However, this lacks robust clinical trial data.
Novel agents: SCY-247 (second-generation triterpenoid) shows promise in preclinical studies, maintaining activity against echinocandin-resistant C. glabrata 5, but is not yet clinically available.
Critical Management Steps
Confirm resistance: Perform susceptibility testing for both azoles and echinocandins on all C. glabrata isolates 1. Testing for echinocandin susceptibility is specifically recommended for patients with prior echinocandin exposure or C. glabrata infection.
Source control: Remove central venous catheters within 48–72 hours if safely possible 6. For intra-abdominal or other focal infections, surgical drainage or debridement is essential.
Monitor response: Obtain daily or every-other-day blood cultures until three consecutive negative results 6. Persistent fungemia beyond day 5 should prompt re-evaluation for uncontrolled sources.
Ophthalmologic examination: All non-neutropenic patients require dilated fundoscopic examination within the first week to exclude endophthalmitis 1.
Common Pitfalls
- Continuing ineffective therapy: Do not persist with fluconazole or echinocandins once dual resistance is documented, even if the patient appears clinically stable
- Inadequate amphotericin B dosing: Use full doses (3–5 mg/kg) of lipid formulations; lower doses may be subtherapeutic
- Premature discontinuation: Continue therapy for minimum 2 weeks after clearance, not just clinical improvement
- Ignoring site-specific considerations: For urinary tract infections or prostatic/scrotal abscesses, liposomal amphotericin B may have advantages over echinocandins due to better tissue penetration 7
Monitoring and Toxicity
Amphotericin B formulations require:
- Baseline and serial monitoring of renal function, electrolytes (particularly potassium and magnesium), and complete blood counts
- Lipid formulations have significantly reduced nephrotoxicity compared to conventional amphotericin B deoxycholate 1
- Premedication with acetaminophen and diphenhydramine may reduce infusion-related reactions
The 2025 ECMM/ISHAM/ASM global guideline reinforces that lipid formulation amphotericin B remains the backbone for resistant invasive candidiasis when other options are exhausted 6.