Macrophage internalization creates a multidrug-tolerant fungal persister population, providing a permissive reservoir for the emergence of drug resistance

Abstract

Candida glabratais a major fungal pathogen notable for causing recalcitrant infections, rapid emergence of drug-resistant strains, and its ability to survive and proliferate within macrophages. Resembling bacterial persisters, a subset of genetically drug-susceptibleC. glabratacells can survive lethal exposure to the fungicidal echinocandin drugs. Herein, we show that macrophage internalization induces cidal drug tolerance inC. glabrata, expanding the persister reservoir from which echinocandin-resistant mutants emerge. We show that this drug tolerance is associated with non-proliferation and is triggered by macrophage-induced oxidative stress, and that deletion of genes involved in reactive oxygen species detoxification significantly increases the emergence of echinocandin-resistant mutants. Finally, we show that the fungicidal drug amphotericin B can kill intracellularC. glabrataechinocandin persisters, reducing emergence of resistance. Our study supports the hypothesis that intra-macrophageC. glabratais a reservoir of recalcitrant/drug-resistant infections, and that drug alternating strategies can be developed to eliminate this reservoir.

OverlookedCandida glabratapetites are echinocandin tolerant, induce host inflammatory responses, and display poorin vivofitness

“…In addition, similar to antibiotic tolerant cells, petite isolates harbored mutations in multiple genes potentially underpinning echinocandin tolerance. The parental strains, however, showed the hallmark of echinocandin persisters, as described previously (36). Of note, both phenomena are distinct from the concept of azole tolerance, which refers to slow growth in the presence of static antifungals (42), whereas echinocandin tolerance and persistence refer to survival during exposure to supra-MIC concentrations of cidal antifungal drugs.…”

“…Although echinocandins and amphotericin B are both cidal antifungal drugs, echinocandins' cidality requires actively growing cells producing a cell wall, whereas amphotericin B indistinguishably kills growing and non-growing cells (36). Altogether, these observations suggest that petites have a fitness benefit relative to non-petites when exposed to echinocandin drugs but are killed as effectively as non-petite cells by polyene amphotericin B.…”

A multidimensional assessment of in-host fitness costs of drug resistance in the opportunistic fungal pathogenCandida glabrata

“…Collectively, our dual-RNAseq and multiple in vivo mouse models shed light on the fitness cost associated with drug resistant C. glabrata isolates and suggest that such fitness costs could be offset in macrophagerich niches, which may also act as a reservoir for the emergence and enrichment of drug resistant cells (40).…”

“We've got to get out”—Strategies of human pathogenic fungi to escape from phagocytes

“…Moreover, C. glabrata was found to be surrounded by monocytes and even inside mononuclear cells in immunocompetent mice, and notably could still be isolated from organs four weeks after infection (Jacobsen et al, 2010). Initial evidence for the intracellular persistence of C. glabrata has recently been provided, showing that the fungus can survive and replicate within THP1-derived macrophages for up to five days (Arastehfar et al, 2023) and within primary macrophages for at least seven days (Siscar-Lewin et al, 2021). How C. glabrata initiates this persistence in macrophages and what fungal processes are required remains to be determined.…”

“…For fungi that use macrophages to hide from the immune response and persist, a rapid and efficient clearance by pharmacological treatment is crucial. In the case of C. glabrata , it has been shown that it develops increased tolerance to antifungal drugs during its intracellular persistence (Arastehfar et al, 2023; Siscar‐Lewin et al, 2021). A similar mechanism was shown for A. terreus conidia that escape antifungal treatment by persisting in dendritic cells (Hsieh et al, 2017a).…”