Antifungal Susceptibility Profiles and Drug Resistance Mechanisms of Clinical Lomentospora prolificans Isolates

Fusarium species,Scedosporium species, and Lomentospora prolificans: A systematic review to inform the World Health Organization priority list of fungal pathogens

Recognizing the growing global burden of fungal infections, the World Health Organization established a process to develop a priority list of fungal pathogens (FPPL). In this systematic review, we aimed to evaluate the epidemiology and impact of infections caused by Fusarium spp., Scedosporium spp., and Lomentospora prolificans to inform the first FPPL. PubMed and Web of Sciences databases were searched to identify studies published between January 1, 2011 and February 23, 2021, reporting on mortality, complications and sequelae, antifungal susceptibility, preventability, annual incidence, and trends. Overall, 20, 11, and 9 articles were included for Fusarium spp., Scedosporium spp., and L. prolificans, respectively. Mortality rates were high in those with invasive fusariosis, scedosporiosis, and lomentosporiosis (42.9%-66.7%, 42.4%-46.9%, and 50.0%-71.4%, respectively). Antifungal susceptibility data, based on small isolate numbers, showed high minimum inhibitory concentrations (MIC)/minimum effective concentrations for most currently available antifungal agents. The median/mode MIC for itraconazole and isavuconazole were ≥16 mg/l for all three pathogens. Based on limited data, these fungi are emerging. Invasive fusariosis increased from 0.08 cases/100 000 admissions to 0.22 cases/100 000 admissions over the time periods of 2000-2009 and 2010-2015, respectively, and in lung transplant recipients, Scedosporium spp. and L. prolificans were only detected from 2014 onwards. Global surveillance to better delineate antifungal susceptibility, risk factors, sequelae, and outcomes is required.

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.

Disseminated Infection by Scedosporium/Lomentospora during Induction Therapy for Acute Myeloid Leukemia Complicated by Nontuberculous Mycobacteria

Scedosporium/Lomentospora infections are rare and are associated with a high mortality rate in immunocompromised patients. A 69-year-old man with nontuberculous mycobacteria (NTM) died during induction chemotherapy for acute myeloid leukemia because of multiple organ failure due to pneumonia. During an autopsy, Lomentospora prolificans was detected using a fungal gene analysis of the blood, lungs, spleen, kidneys, and intestines, and Scedosporium aurantiacum was detected in the lungs. NTM disease may predispose patients to Scedosporium/Lomentospora infections. Physicians should consider Scedosporium/Lomentospora spp. as an invasive fungal infection that occurs during myelosuppression, particularly when NTM is a complication.

Evolutionary trends in antifungal resistance: a meta-analysis

The present paper includes a meta-analysis of literature data on 318 species of fungi belonging to 34 orders in their response to 8 antifungal agents (amphotericin B, caspofungin, fluconazole, itraconazole, ketoconazole, posaconazole, terbinafine, and voriconazole). Main trends of MIC results at the ordinal level were visualized. European Committee on Antimicrobial Susceptibility Testing and Clinical & Laboratory Standards Institute (CLSI) clinical breakpoints were used as the staff gauge to evaluate MIC values ranging from resistance to susceptibility, which were subsequently compared with a phylogenetic tree of the fungal kingdom. Several orders (Hypocreales, Microascales, and Mucorales) invariably showed resistance. Also the basidiomycetous orders Agaricales, Polyporales, Sporidiales, Tremellales, and Trichosporonales showed relatively high degrees of azole multi-resistance, while elsewhere in the fungal kingdom, including orders with numerous pathogenic and opportunistic species, that is, Onygenales, Chaetothyiales, Sordariales, and Malasseziales, in general were susceptible to azoles. In most cases, resistance vs susceptibility was consistently associated with phylogenetic distance, members of the same order showing similar behavior.

IMPORTANCE

A kingdom-wide the largest set of published wild-type antifungal data comparison were analyzed. Trends in resistance in taxonomic groups (monophyletic clades) can be compared with the phylogeny of the fungal kingdom, eventual relationships between fungus-drug interaction and evolution can be described.

A systematic review and disability-adjusted life years of Scedosporium/Lomentospora infection in patients after near-drowning

Scedosporium/Lomentospora species exist as saprophytic moulds that can potentially lead to serious infections in patients who have experienced near-drowning incidents. Scedosporium species are distributed across different regions of the world while Lomentospora prolificans has quite a restricted geographic distribution. We aimed to systematically review scedosporiosis cases after near-drowning, their clinical manifestations, underlying diseases, treatments, outcomes and its impact through disability-adjusted life years (DALYs). Five available sources were searched from 1 January 2007, to 20 April 2022. Thirty-eight studies, including 41 patients, were evaluated. Mean age was 33.6 ± 18.6 years (range 1-68), and 28 were male (68.3%). Central nervous system (CNS) dissemination predominated (36/41; 87.8%), presenting mainly as multiple brain abscesses (26/41; 63.4%), followed by lung involvement (22/41; 56.4%). Scedosporium apiospermum species complex was the most causative agent (38/41; 92.7%). Overall mortality was 51.2%. Half of the patients (18/37) were cured after receiving proper treatment, and in most cases, voriconazole alone or in combination with surgery or other antifungals caused survival. The mean survival time was 123 ± 27 days. Mean DALYs in 1980-2022 were 46.110 ± 3.318 (39.607-52.612). Time to diagnosis was estimated to be 120 days, and there was no association between time to diagnosis and outcome. Voriconazole is a potentially effective therapy, and combination of surgery and antifungal treatment may lead to more favourable outcome. Advances in early diagnosis and appropriate antifungal therapy may have contributed to reducing its mortality.

Miltefosine repositioning: A review of potential alternative antifungal therapy

Fungal infections are a global health problem with high mortality and morbidity rates. Available antifungal agents have high toxicity and pharmacodynamic and pharmacokinetic limitations. Moreover, the increased incidence of antifungal-resistant isolates and the emergence of intrinsically resistant species raise concerns about seeking alternatives for efficient antifungal therapy. In this context, we review literature data addressing the potential action of miltefosine (MFS), an anti-Leishmania and anticancer agent, as a repositioning drug for antifungal treatment. Here, we highlight the in vitro and in vivo data, MFS possible mechanisms of action, case reports, and nanocarrier-mediated MFS delivery, focusing on fungal infection therapy. Finally, many studies have demonstrated the promising antifungal action of MFS in vitro, but there is little or no data on antifungal activity in vertebrate animal models and clinical trials, so have a need to develop more research for the repositioning of MFS as an antifungal therapy.

In Vitro and In Vivo Effect of the Imidazole Luliconazole against Lomentospora prolificans and Scedosporium spp

Infections with Scedosporium spp. and Lomentospora prolificans have become a serious threat in clinical settings. The high mortality rates associated with these infections can be correlated with their multidrug resistance. The development of alternative treatment strategies has become crucial. Here, we investigate the in vitro and in vivo activity of luliconazole (LLCZ) against Scedosporium apiospermum (including its teleomorph Pseudallescheria boydii) and Lomentospora prolificans. The LLCZ MICs were determined for a total of 37 isolates (31 L. prolificans isolates, 6 Scedosporium apiospermum/P. boydii strains) according to EUCAST. Furthermore, the LLCZ antifungal activity was tested in vitro, using an XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide salt] growth kinetics assay and biofilm assays (crystal violet and XTT assay). In addition, a Galleria mellonella infection model was used for in vivo treatment assays. The MIC90 of LLCZ was determined to be 0.25 mg/L for all tested pathogens. Growth was inhibited within 6 to 48 h of the start of incubation. LLCZ inhibited biofilm formation in both preadhesion stages and late-stage adhesion. In vivo, a single dose of LLCZ increased the survival rate of the larvae by 40% and 20% for L. prolificans and Scedosporium spp., respectively. This is the first study demonstrating LLCZ activity against Lomentospora prolificans in vitro and in vivo and the first study showing the antibiofilm effect of LLCZ in Scedosporium spp. IMPORTANCE Lomentospora prolificans and S. apiospermum/P. boydii are opportunistic, multidrug-resistant pathogens causing invasive infections in immunosuppressed patients and sometimes in healthy persons. Lomentospora prolificans is panresistant against the currently available antifungals, and both species are associated with high mortality rates. Thus, the discovery of novel antifungal drugs exhibiting an effect against these resistant fungi is crucial. Our study shows the effect of luliconazole (LLCZ) against L. prolificans and Scedosporium spp. in vitro, as well as in an in vivo infection model. These data reveal the previously unknown inhibitory effect of LLCZ against L. prolificans and its antibiofilm effect in Scedosporium spp. It represents an extension of the literature regarding azole-resistant fungi and could potentially lead to the development of future treatment strategies against these opportunistic fungal pathogens.

Diagnosis and Treatment of Fungal Infections in Lung Transplant Recipients

Fungal infections are a significant source of morbidity in the lung transplant population via direct allograft damage and predisposing patients to the development of chronic lung allograft dysfunction. Prompt diagnosis and treatment are imperative to limit allograft damage. This review article discusses incidence, risk factors, and symptoms with a specific focus on diagnostic and treatment strategies in the lung transplant population for fungal infections caused by Aspergillus, Candida, Coccidioides, Histoplasma, Blastomyces, Scedosporium/Lomentospora, Fusarium, and Pneumocystis jirovecii. Evidence for the use of newer triazole and inhaled antifungals to treat isolated pulmonary fungal infections in lung transplant recipients is also discussed.

The challenges of the genome-based identification of antifungal resistance in the clinical routine

The increasing number of chronic and life-threatening infections caused by antimicrobial resistant fungal isolates is of critical concern. Low DNA sequencing cost may facilitate the identification of the genomic profile leading to resistance, the resistome, to rationally optimize the design of antifungal therapies. However, compared to bacteria, initiatives for resistome detection in eukaryotic pathogens are underdeveloped. Firstly, reported mutations in antifungal targets leading to reduced susceptibility must be extensively collected from the literature to generate comprehensive databases. This information should be complemented with specific laboratory screenings to detect the highest number possible of relevant genetic changes in primary targets and associations between resistance and other genomic markers. Strikingly, some drug resistant strains experience high-level genetic changes such as ploidy variation as much as duplications and reorganizations of specific chromosomes. Such variations involve allelic dominance, gene dosage increments and target expression regime effects that should be explicitly parameterized in antifungal resistome prediction algorithms. Clinical data indicate that predictors need to consider the precise pathogen species and drug levels of detail, instead of just genus and drug class. The concomitant needs for mutation accuracy and assembly quality assurance suggest hybrid sequencing approaches involving third-generation methods will be utilized. Moreover, fatal fast infections, like fungemia and meningitis, will further require both sequencing and analysis facilities are available in-house. Altogether, the complex nature of antifungal resistance demands extensive sequencing, data acquisition and processing, bioinformatic analysis pipelines, and standard protocols to be accomplished prior to genome-based protocols are applied in the clinical setting.

Decoding the antifungal resistance mechanisms in biofilms of emerging, ubiquitous and multidrug-resistant species belonging to the Scedosporium/Lomentospora genera

The opportunistic filamentous fungi belonging to the Scedosporium and Lomentospora genera are highly tolerant to all classes of available antifungal drugs. Moreover, the mature biofilm formed by these fungi presents higher antifungal resistance when compared to planktonic cells. Nevertheless, the resistance mechanisms developed by the biofilm lifestyle are not completely elucidated. In the current study, we have investigated the mainly known resistance mechanisms to azoles (voriconazole and fluconazole) and polyenes (amphotericin B - AMB) in S. apiospermum, S. minutisporum, S. aurantiacum, and L. prolificans (formerly S. prolificans) biofilms. Both classes of antifungals can physically bind to the extracellular matrix of mature biofilms, preventing the drugs from reaching their targets on biofilm-forming cells, which precludes their activity and toxicity. In addition, the activity of efflux pumps, measured by Rhodamine 6 G, was increased along the maturation of the biofilm. The efflux pump's inhibition by L-Phe-L-Arg-β-naphthylamide culminated in a 2- to 16-fold increase in azole susceptibility in conidial cells, but not in mature biofilms. Finally, we demonstrated by using specific inhibitors that in conidia, but not in biofilms, AMB induced the production of reactive oxygen species through the activity of the oxidative phosphorylation system (complex I to IV and alternative oxidases). However, the cellular redox imbalance caused by AMB was well coped with the high activity of antioxidative enzymes, such as superoxide dismutase and catalase. Altogether, our results revealed that Scedosporium/Lomentospora biofilm resistance occurs through various mechanisms that operate concomitantly, which could explain the huge challenge in the clinical treatment of scedosporiosis/lomentosporiosis.

The synergistic effect of minocycline and azole antifungal drugs against Scedosporium and Lomentospora species

Background

This study was aimed to determine the potency of Minocycline (MIN) and azoles, including itraconazole (ITR), voriconazole (VOR) and posaconazole (POS) against Scedosporium and Lomentospora species.

Results

This study revealed that MIN exhibited no significant antifungal activity against any of the tested strains, whereas in vitro combination of MIN with ITR, VOR or POS showed satisfactory synergistic effects against 8 (80%), 1 (10%), and 9 (90%) strains, respectively. Moreover, combined use of MIN with azoles decreased the minimum inhibitory concentration (MIC) range from 5.33–16 μg/ml to 1–16 μg/ml for ITR, from 0.42–16 μg/ml to 0.21–16 μg/ml for VOR, and from 1.33–16 μg/ml to 0.33–16 μg/ml for POS. Meanwhile, no antagonistic interactions were observed between the above combinations. The G. mellonella infection model demonstrated the in vivo synergistic antifungal effect of MIN and azoles.

Conclusions

The present study demonstrated that combinations between MIN and azoles lead to synergistic antimicrobial effects on Scedosporium and Lomentospora species, while showing a potential for overcoming and preventing azole resistance.

Roles for Structural Biology in the Discovery of Drugs and Agrochemicals Targeting Sterol 14α-Demethylases

Antifungal drugs and antifungal agrochemicals have significant limitations. These include several unintended consequences of their use including the growing importance of intrinsic and acquired resistance. These problems underpin an increasingly urgent need to improve the existing classes of antifungals and to discover novel antifungals. Structural insights into drug targets and their complexes with both substrates and inhibitory ligands increase opportunity for the discovery of more effective antifungals. Implementation of this promise, which requires multiple skill sets, is beginning to yield candidates from discovery programs that could more quickly find their place in the clinic. This review will describe how structural biology is providing information for the improvement and discovery of inhibitors targeting the essential fungal enzyme sterol 14α-demethylase.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.