Bad to the bone: Candida (Candidozyma) auris vertebral osteomyelitis treated with combination antifungal therapy followed by a novel long-acting echinocandin.

Background: Candida auris is an emerging multidrug-resistant yeast associated with healthcare-associated infections and high mortality. Vertebral osteomyelitis due to Candida auris is rare and challenging to treat due to limited data on antifungal bone penetration, prolonged treatment duration, and resistance to multiple antifungal classes. Long-acting agents such as rezafungin may offer promising outpatient options, though clinical experience remains limited. Case Summary: A 70-year-old male developed vertebral osteomyelitis/discitis at T3-T4 due to Candida auris, following multiple catheter-related bloodstream infections and C. auris candidemia. Initial treatment included dual antifungal therapy with liposomal amphotericin B and micafungin, selected based on in vitro susceptibility and preclinical synergy data. Therapy was complicated by severe electrolyte disturbances, requiring early discontinuation of amphotericin B. He transitioned to rezafungin and completed nearly 3 months of treatment at home, contributing to a total of 6 months of antifungal therapy in alignment with IDSA guidelines. Rezafungin was generally well tolerated, with only mild hypokalemia and episodic migraine-like symptoms. The patient achieved complete clinical recovery with the resolution of symptoms and normalization of inflammatory markers. No relapse was reported at the 6-month follow-up. Conclusion: This case highlights the complexity of managing invasive Candida auris osteomyelitis and underscores the utility of dual antifungal combination therapy to enhance efficacy and potentially prevent the development of resistance during the intensive phase of treatment. It also demonstrates the feasibility of using rezafungin as an option for long-term outpatient management. Given the limited clinical experience with combination therapy and rezafungin use, further data are needed to inform standardized treatment approaches.