Background: Ibrexafungerp (SCY-078) is the newest oral and intravenous antifungal drug with broad activity, currently undergoing clinical trials for invasive candidiasis.Objective: The aim of this study was to assess the in vitro activity of ibrexafungerp and comparators against a collection of 434 European blood isolates of Candida.Methods: Ibrexafungerp, caspofungin, fluconazole, and micafungin minimum inhibitory concentrations (MICs) were collected from 12 European laboratories for 434 blood isolates, including 163 Candida albicans, 108 Candida parapsilosis, 60 Candida glabrata, 40 Candida tropicalis, 29 Candida krusei, 20 Candida orthopsilosis, 6 Candida guilliermondii, 2 Candida famata, 2 Candida lusitaniae, and 1 isolate each of Candida bracarensis, Candida catenulata, Candida dubliniensis, and Candida kefyr. MICs were determined by the EUCAST broth microdilution method, and isolates were classified according to recommended clinical breakpoints and epidemiological cutoffs. Additionally, 22 Candida auris from different clinical specimens were evaluated.Results: Ibrexafungerp MICs ranged from 0.016 to ≥8 mg/L. The lowest ibrexafungerp MICs were observed for C. albicans (geometric MIC 0.062 mg/L, MIC range 0.016–0.5 mg/L) and the highest ibrexafungerp MICs were observed for C. tropicalis (geometric MIC 0.517 mg/L, MIC range 0.06–≥8 mg/L). Modal MICs/MIC₅₀s (mg/L) against Candida spp. were 0.125/0.06 for C. albicans, 0.5/0.5 for C. parapsilosis, 0.25/0.25 for C. glabrata, 0.5/0.5 for C. tropicalis, 1/1 for C. krusei, 4/2 for C. orthopsilosis, and 0.5/0.5 for C. auris. Ibrexafungerp showed activity against fluconazole- and echinocandin-resistant isolates. If adopting wild-type upper limits, a non-wild-type phenotype for ibrexafungerp was only observed for 16/434 (3.7%) isolates: 11 (4.6%) C. parapsilosis, 4 (5%) C. glabrata, and 1 (2.5%) C. tropicalis.Conclusion: Ibrexafungerp showed a potent in vitro activity against Candida.

Mycobacterium abscessus is an opportunistic pathogen that mainly colonizes and infects cystic fibrosis patients’ lungs. M. abscessus is naturally resistant to many antibiotics such as rifamycin, tetracyclines and β-lactams. The current therapeutic regimens are not very effective and are mostly based on repurposed drugs used against Mycobacterium tuberculosis infections. Thus, new approaches and novel strategies are urgently needed. This review aims to provide an overview of the latest ongoing findings to fight M. abscessus infections by analyzing emerging and alternative treatments, novel drug delivery strategies, and innovative molecules.

Soil organisms exhibit high tolerance to heavy metals, probably acquired through evolutionary adaptation to contaminated environments. Essentially, metal tolerance in fungi involves several specific and non-specific mechanisms that include metal efflux, metal binding to cell walls, extracellular and intracellular sequestration and complexation with proteins. However, fungi have adopted different strategies to detoxify heavy metals, although species differ in the mechanisms used. In this complex molecular framework, metallothioneins (MTs) are becoming increasingly relevant in metal homeostasis, even though little is known about their role in metal adaptation and virulence in fungal pathogens. With the aim to decipher the function of metallothioneins in the opportunistic fungus Fusarium oxysporum, we have carried out an in silico analysis that revealed the presence of a hypothetical metallothionein (mt1) that has multiple metal responsive elements in its promoter region and conserved cysteine motifs in its coding sequence. Characterization of strain Δmt1 deficient in the mt1 gene revealed higher sensitivity of this mutant to copper, cadmium and zinc compared to the wild type strain (wt). Expression analyses revealed that Zn specifically activates mt1, but the lack of this gene did not lead to a transcriptional up-regulation of genes gapdh and prx, associated with the oxidative stress response. The lack of mt1 did not alter the pathogenic capacity of the fungus, either in tomato plant or in a murine model of systemic infection. Nevertheless, Δmt1 displayed lower resistance to macrophage killing, suggesting a connection between the absence of mt1 and impaired defence capacity against copper and reactive oxygen species.

DNA N6-adenine methylation (6mA) has recently gained importance as an epigenetic modification in eukaryotes. Its function in lineages with high levels, such as early-diverging fungi (EDF), is of particular interest. Here, we investigated the biological significance and evolutionary implications of 6mA in EDF, which exhibit divergent evolutionary patterns in 6mA usage. The analysis of two Mucorales species displaying extreme 6mA usage reveals that species with high 6mA levels show symmetric methylation enriched in highly expressed genes. In contrast, species with low 6mA levels show mostly asymmetric 6mA. Interestingly, transcriptomic regulation throughout development and in response to environmental cues is associated with changes in the 6mA landscape. Furthermore, we identify an EDF-specific methyltransferase, likely originated from endosymbiotic bacteria, as responsible for asymmetric methylation, while an MTA-70 methylation complex performs symmetric methylation. The distinct phenotypes observed in the corresponding mutants reinforced the critical role of both types of 6mA in EDF.

Cu is an essential trace element for cell growth and proliferation. However, excess of Cu accumulation leads to cellular toxicity. Thus, precise and tight regulation of Cu homeostasis processes, including transport, delivery, storage, detoxification, and efflux machineries, is required. Moreover, the maintenance of Cu homeostasis is critical for the survival and virulence of fungal pathogens. Cu homeostasis has been extensively studied in mammals, bacteria, and yeast, but it has not yet been well documented in filamentous fungi. In the present work, we investigated Cu tolerance in the filamentous fungus Fusarium oxysporum by analysing the Cu transporter coding gene crpF, previously studied in Aspergillus fumigatus. The expression studies demonstrated that crpF is upregulated in the presence of Cu and its deletion leads to severe sensitivity to low levels of CuSO₄ in F. oxysporum. Targeted deletion of crpF did not significantly alter the resistance of the fungus to macrophage killing, nor its pathogenic behaviour on the tomato plants. However, the targeted deletion mutant ΔcrpF showed increased virulence in a murine model of systemic infection compared to wild-type strain (wt).

Mucorales are the causal agents for the lethal disease known as mucormycosis. Mortality rates of mucormycosis can reach up to 90%, due to the mucoralean antifungal drug resistance and the lack of effective therapies. A concerning urgency among the medical and scientific community claims to find targets for the development of new treatments. Here, we reviewed different studies describing the role and machinery of a novel non-canonical RNAi pathway (NCRIP) only conserved in Mucorales. Its non-canonical features are the independence of Dicer and Argonaute proteins. Conversely, NCRIP relies on RNA-dependent RNA Polymerases (RdRP) and an atypical ribonuclease III (RNase III). NCRIP regulates the expression of mRNAs by degrading them in a specific manner. Its mechanism binds dsRNA but only cuts ssRNA. NCRIP exhibits a diversity of functional roles. It represses the epimutational pathway and the lack of NCRIP increases the generation of drug resistant strains. NCRIP also regulates the control of retrotransposons expression, playing an essential role in genome stability. Finally, NCRIP regulates the response during phagocytosis, affecting the multifactorial process of virulence. These critical NCRIP roles in virulence and antifungal drug resistance, along with its exclusive presence in Mucorales, mark this pathway as a promising target to fight against mucormycosis.