Fungicidal activity of human antimicrobial peptides and their synergistic interaction with common antifungals against multidrug-resistant Candida auris

Abstract

Emergence of Candida auris, a multidrug resistant yeast, demonstrates the urgent need for novel antifungal agents. Human antimicrobial peptides (AMP) are naturally occurring molecules with wide spectrum antimicrobial activity, particularly against a variety of fungi. Therefore, this study examined the antifungal activity of seven different human AMPs against C. auris following the CLSI guidelines. The antifungal activity was further assessed using time kill curve and cell viability assays. For combination interaction, effectiveness of these peptides with three antifungals, uconazole, amphotericin B and caspofungin, was done following standard protocols. To elucidate the antifungal mechanism, the effects of peptides on membrane permeability was investigated using propidium iodide staining method and confocal imaging. Antifungal susceptibility results showed that all the examined peptides possessed fungicidal effect against C. auris at different levels, with human β-Defensin-3 being the most potent antifungal with MIC values ranging from 3.125-12.5 µg/ml. Time kill curves further con rmed the killing effect of all the tested peptides. Viability assay showed a signi cant decrease in the percentage of viable cells exposed to different inhibitory and fungicidal concentrations of each peptide (p < 0.01). Furthermore, peptides showed mostly synergistic interaction when combined with conventional antifungal drugs, with caspofungin showing 100% synergy when combined with different AMPs. As antifungal mechanism, peptides disrupted the membrane permeability at concentrations that correlated with the inhibition of growth. Overall, the ndings of this study point towards the application of the tested peptides as a monotherapy or as a combination therapy with antifungal drugs to treat multidrug resistant C. auris infections.

Antifungal activity of human antimicrobial peptides targeting apoptosis in Candida auris

“…Considering this, AMPs have been suggested as the most promising candidates for combating antifungal resistance [28]. Previously, we have shown that particular human AMPs exhibited fungicidal activity against C. auris and altered its membrane permeability as a mechanism of action [19]. Several studies, however, have revealed that many AMPs with membrane-interacting effects exhibit additional mechanisms such as induction of apoptosis [29].…”

“…Table 1 illustrates the MIC and MFC results for peptides and antifungals against two C. auris isolates, which were determined in this research and in prior study [19]. The antifungals (fluconazole, amphotericin B and caspofungin) were initially used to further confirm the susceptibility pattern of the tested strains and determine test concentration for further experiments.…”

“…Previously, in our research, selected human defensins and histatin 5 (His 5) were shown to have remarkable fungicidal activity against C. auris . Moreover, they increased the cell-membrane permeability as a part of their mechanism of action, nevertheless, this may not be sufficient to cause cell death [19].…”

Current Perspectives of Antifungal Therapy: A Special Focus on <em>Candida auris</em>

“…Human body is also a potent source of antifungal peptides, so far many peptides with different biological functions were reported from the human body. Peptides like human β-defensin-3 [72], human cathelicidin peptides LL-37 [73] and salivary histatin-5 [74] were recently reported with antifungal activity on C. auris (Table 3). Human β-defensin-3 and cathelicidin peptides LL-37 produced 100% and 70% of synergy with fluconazole [72,73].…”

Synergistic action of synthetic peptides and amphotericin B causes disruption of the plasma membrane and cell wall in Candida albicans

“…They exhibit broad-ranging antimicrobial activity and are particularly effective against many strains of fungi. Several research efforts have focused on investigating the synergistic combination of these peptides with commercial antifungals, with the aim of creating new therapeutic agents that not only increase efficacy but also decrease the occurrence of adverse effects [ 2 , 7 , 8 ].…”