The impact of the fluconazole trailing effect on the persistence of Candida albicans bloodstream infection when treated with fluconazole

Tolerance and heteroresistance to echinocandins in Candida auris: conceptual issues, clinical implications, and outstanding questions

Candida auris is a significant public health threat due to its environmental persistence and multidrug resistance, with echinocandins being the preferred treatment. However, in addition to resistance, echinocandin tolerance and heteroresistance may contribute to treatment challenges. Echinocandin tolerance involves reduced drug-mediated killing, while heteroresistance is the ability of a small cell subset to grow at high drug concentrations. These phenomena may facilitate the emergence of full resistance and complicate clinical outcomes. The clinical significance of these mechanisms remains unclear, with limited data correlating them with treatment failures. Research is needed to understand their mechanisms and impact, develop streamlined and robust methods to detect them in clinical settings, and explore mitigation strategies. The pathogen's range of drug adaptations demands innovative approaches like spatial transcriptomics to dissect these complex responses and improve patient outcomes.

Adaptive morphological changes link to poor clinical outcomes by conferring echinocandin tolerance in Candida tropicalis

Antibiotic tolerance, by which susceptible bacteria survive at high bactericide doses, is known to cause treatment failure in clinical practice. However, the impact of antifungal tolerance on clinical outcomes remains poorly understood. Here, we observed that candidemia cases caused by echinocandin-tolerant Candida tropicalis exhibited higher mortality rates during caspofungin treatment by conducting a comprehensive seven-year retrospective analysis. C. tropicalis develops tolerance to caspofungin by forming multicellular aggregates, a process linked to defects in cell division, both in vitro and in vivo. Our omics-based profiling results reveal that C. tropicalis develops tolerance through the intricate modulation of cell wall integrity and cell division pathways, particularly through the activation of chitin synthesis and the downregulation of cell division-related genes. The overexpression of cell division-related factor Ace2 can suppress the tolerance of C. tropicalis to caspofungin by delaying the formation of multicellular aggregates. Moreover, calcineurin inhibitors can suppress the tolerance of C. tropicalis by disrupting these adaptive molecular changes, thereby significantly enhancing the antifungal efficacy of caspofungin in a Galleria mellonella model. Collectively, our findings provide evidence that C. tropicalis acquires echinocandin tolerance through morphological alterations, and that inhibiting calcineurin may be a promising method to reduce this tolerance.