Paradoxical Growth of Candida albicans in the Presence of Caspofungin Is Associated with Multiple Cell Wall Rearrangements and Decreased Virulence

Abstract

In the last decade, echinocandins have emerged as an important family of antifungal drugs because of their fungicidal activity against Candida spp. Echinocandins inhibit the enzyme ␤-1,3-D-glucan synthase, encoded by the FKS genes, and resistance to echinocandins is associated with mutations in this gene. In addition, echinocandin exposure can produce paradoxical growth, defined as the ability to grow at high antifungal concentrations but not at intermediate concentrations. In this work, we have demonstrated that paradoxical growth of Candida albicans in the presence of caspofungin is not due to antifungal degradation or instability. Media with high caspofungin concentrations recovered from wells where C. albicans showed paradoxical growth inhibited the growth of a Candida krusei reference strain. Cells exhibiting paradoxical growth at high caspofungin concentrations showed morphological changes such as enlarged size, abnormal septa, and absence of filamentation. Chitin content increased from the MIC to high caspofungin concentrations. Despite the high chitin levels, around 23% of cells died after treatment with caspofungin, indicating that chitin is required but not sufficient to protect the cells from the fungicidal effect of caspofungin. Moreover, we found that after paradoxical growth, ␤-1,3-glucan was exposed at the cell wall surface. Cells grown at high caspofungin concentrations had decreased virulence in the invertebrate host Galleria mellonella. Cells grown at high caspofungin concentrations also induced a proinflammatory response in murine macrophages compared to control cells. Our work highlights important aspects about fungal adaptation to caspofungin, and although this adaptation is associated with reduced virulence, the clinical implications remain to be elucidated. Candidemia is a frequent disease among immunosuppressed patients that is caused by opportunistic fungal pathogens from the genus Candida. Candida albicans is the most abundant species found in invasive candidiasis, although an increase in the abundance of other non-albicans Candida species has been described in the last years (1, 2). Echinocandin administration constitutes the main treatment for this disease. Currently, three echinocandins drugs, caspofungin (CAS), micafungin, and anidulafungin, are available for clinical practice. These antifungals are fungicidal against most Candida species and are effective against Candida isolates that are resistant to other antifungals (3). Echinocandins are lipopeptides that inhibit the activity of ␤-1,3-Dglucan synthase, which is encoded by FKS genes (4).Resistance to echinocandins has been described at a low frequency. The main resistance mechanism is associated with mutations in two regions of the FKS gene, denoted hot spot (HS) regions. These mutations result in proteins with reduced affinity for the antifungal (2, 5-7). However, in addition, there are other situations in which yeasts can grow in the presence of the antifungal. In particular, paradoxical growth (PG) (also known as the Eagle ef...

Structure-Activity Relationship Study of the Plant-Derived Decapeptide OSIP108 Inhibiting Candida albicans Biofilm Formation

“…Paradoxical biofilm formation is defined as a resurgence of biofilm formation (Ն50% relative to control treatment) at peptide concentrations above the BIC-2 (17). A similar paradoxical effect of caspofungin has been observed on C. albicans biofilms and planktonic cells (17,18); this effect was found to be associated with multiple cell wall rearrangements and calcineurin-mediated signaling pathways in planktonic C. albicans cells (18,19). Wiederhold and colleagues showed higher MKC1 expression in C. albicans planktonic cells treated with caspofungin concentrations leading to this paradoxical growth phenomenon compared to fungicidal caspofungin concentrations (19).…”

Impact of multi-metals (Cd, Pb and Zn) exposure on the physiology of the yeast Pichia kudriavzevii

“…It was also shown that the exposure to the antifungal caspofungin induced chitin accumulation in the cell wall of different Candida species, including C. krusei. It was proposed that the raise of chitin content and cell wall rearrangements are mechanisms of adaptation (tolerance), which resulted in the decrease of cell wall permeability and susceptibility to the drug (Rueda et al 2014;Walker et al 2013). Thus, in order to understand the physiological responses of P. kudriavzevii to heavy metals exposure, the impact of metals mixture on yeast cell wall was evaluated.…”

An alternative host model of a mixed fungal infection by azole susceptible and resistantAspergillusspp strains

“…26 Three larvae per group were longitudinally sectioned and fixed for 24 h in 4% buffered formalin and dehydrated with increasing concentrations of ethanol (70%, 80%, 90%, 96% and 100%). The samples were then treated with xylene and paraffin embedded.…”