Successful treatment of disseminated disease due to highly resistant Aspergillus calidoustus with a novel antifungal therapy

Genome-Wide Exploration of Thiamin Pyrophosphate Riboswitches in Medically Relevant Fungi Reveals Diverse Distribution and Implications for Antimicrobial Drug Targeting

The rising incidence of fungal infections coupled with limited treatment options underscores the urgent need for novel antifungal therapies. Riboswitches, particularly thiamin pyrophosphate (TPP) class, have emerged as promising antimicrobial targets. This study presents a comprehensive genome-wide analysis of TPP riboswitches in 156 medically relevant fungi utilizing advanced covariance models (CMs) tailored for fungal sequences. Our investigation identified 378 conserved TPP riboswitch sequences distributed across 140 distinct species, revealing a broader prevalence than that previously recognized. Notably, we provide evidence for a novel putative group of TPP riboswitches, designated TPPswSUGAR, associated with sugar transporters in Mucoromycota and Basidiomycota. This group exhibits distinctive structural features while maintaining key TPP-binding motifs, potentially expanding our understanding of the riboswitch diversity in fungi. Our analysis highlights the impact of P3 stem variability on riboswitch detection and characterization, demonstrating the superiority of fungal-specific CMs over generic models. We observed multiple TPP riboswitches in over 50% of the examined species, including clinically significant pathogens involved in aspergillosis and mucormycosis. Remarkably, Aspergillus latus, a species associated with COVID-19 coinfections, harbors six distinct TPP riboswitch sequences, whereas the extremophilic black fungus Hortaea werneckii possesses nine. These findings not only elucidate the diverse distribution of TPP riboswitches in pathogenic fungi but also emphasize their potential as multifaceted targets for antifungal drug development. By addressing key limitations of previous detection methods and providing insights into riboswitch structural diversity, this study lays a foundation for future investigations into riboswitch-mediated regulation in fungi and the development of novel antifungal strategies.

Aspergillus calidoustus and Talaromyces columbinus infections in chronic graft-versus-host disease

Advancements in allogeneic haematopoietic stem cell transplant (alloHSCT) procedures have improved patient outcomes over the last two decades, though invasive fungal infections (IFIs) remain a significant risk. The incidence of IFIs in alloHSCT recipients is estimated at 6%, with a mortality rate of 13%, and Aspergillus species are the most common pathogens involved. Posaconazole is effective in preventing IFIs post-transplant and is standard care during neutropenia or when managing graft-versus-host disease (GvHD) with high-dose steroids. However, azole prophylaxis may cause resistant Aspergillus species like A. calidoustus, which are difficult to treat. We report a case from our institution where a patient developed a dual infection with Aspergillus calidoustus and Talaromyces columbinus after alloHSCT and posaconazole prophylaxis. While A. calidoustus is known to cause IFIs in HSCT recipients, T. columbinus represents a previously unreported occurrence in medical literature. This case underscores the importance of a multifaceted diagnostic strategy, integrating BAL diagnosis, mycological cultures, direct microscopy, fungal speciation, susceptibility testing, and biomarkers. These comprehensive approaches are indispensable for accurate pathogen identification and effective management of IFIs with appropriate antifungal agents.

A Case of Aspergillus calidoustus Thoracic Spine Osteomyelitis

Aspergillus infections are of significant concern in patients who are immunocompromised, including transplant recipients. Aspergillus calidoustus is an emerging pathogen reported to cause a wide array of infections. We present a case of A. calidoustus thoracic spine osteomyelitis in a patient with an orthotopic heart transplant (OHT). To our knowledge, this is the first case of A. calidoustus osteomyelitis in a patient with OHT.

MicroRNAs in infectious diseases: potential diagnostic biomarkers and therapeutic targets

MicroRNAs (miRNAs) are conserved, short, non-coding RNAs that play a crucial role in the post-transcriptional regulation of gene expression. They have been implicated in the pathogenesis of cancer and neurological, cardiovascular, and autoimmune diseases. Several recent studies have suggested that miRNAs are key players in regulating the differentiation, maturation, and activation of immune cells, thereby influencing the host immune response to infection. The resultant upregulation or downregulation of miRNAs from infection influences the protein expression of genes responsible for the immune response and can determine the risk of disease progression. Recently, miRNAs have been explored as diagnostic biomarkers and therapeutic targets in various infectious diseases. This review summarizes our current understanding of the role of miRNAs during viral, fungal, bacterial, and parasitic infections from a clinical perspective, including critical functional mechanisms and implications for their potential use as biomarkers and therapeutic targets.

Evolution of antifungals for invasive mold infections in immunocompromised hosts, then and now

INTRODUCTION

The current armamentarium of antifungal agents for invasive mold infections (IMI) has dramatically improved over the last 50 years. Existing therapies are, however, associated with toxicities, drug interactions, and in some cases, therapeutic failures. Novel antifungals are needed to address the increasing prevalence of IMI and the growing threat of antifungal resistance.

AREAS COVERED

We review the history and development of the most commonly used antifungals. We discuss the current consensus guidelines and supporting data for treatment of invasive mold infection (IMI), the role of susceptibility testing, and the niche that novel antifungals could fill. We review the current data for aspergillosis, mucormycosis, and hyalohyphomycosis.

EXPERT OPINION

Robust clinical trial data demonstrating the relative effectiveness of our current antifungal agents for treating IMI outside of A. fumigatus remains limited. Clinical trials are urgently needed to delineate the relationship between MICs and clinical outcomes for existing agents and to better evaluate the invitro and in-vivo aspects of antifungal synergy. Continued international multicenter collaboration and standardized clinical endpoints for trials evaluating both existing and new agents is necessary to advance the field.

Case Commentary: Long-term fosmanogepix use in a transplant recipient with disseminated aspergillosis caused by azole-resistant Aspergillus calidoustus

Aspergillus calidoustus is an emerging, azole-resistant, cryptic Aspergillus species in immunosuppressed patients that often features extrapulmonary involvement and carries high mortality. The case presented by J. F. Camargo, R. Jabr, A. D. Anderson, L. Lekakis, et al. (Antimicrob Agents Chemother 66:e02206-21, 2022, https://doi.org/10.1128/aac.02206-21 ) describes a transplant recipient with disseminated A. calidoustus infection who was successfully treated with surgical source control, tapering of immunosuppression, and long-term, combination antifungal treatment that included the first-in-class fosmanogepix, which targets fungal mannoprotein trafficking and anchoring.