Mucormycosis is known to be a rare opportunistic infection caused by Syncephalastrum species, which are Mucorales fungi of the Zygomycetes class. These moulds are rarely involved in clinical diseases and are generally seen as contaminants in the clinical laboratory. However, in recent years, case reports of human infections due to Syncephalastrum have increased, especially in immunocompromised hosts. In this study, we describe two new Syncephalastrum species, which were isolated from human nails and sputum samples from two different patients. We used several methods of genomic and phenotypic characterisation. The phenotypic analysis, relied on morphological features, analysed both by optical and scanning electron microscopy. We used Matrix Assisted Laser Desorption Ionization-Time of Flight mass spectrometry, energy-dispersive X-ray spectroscopy, and BiologTM technology to characterise the proteomic, chemical mapping, and carbon source assimilation profiles, respectively. The genomic analysis relied on multilocus sequence analysis of the rRNA internal transcribed spacers and D1/D2 large-subunit domains, and fragments of the translation elongation factor 1-alpha, and the β-tubulin genes. The two novel species in the genus Syncephalastrum, namely S. massiliense PMMF0073 and S. timoneanum PMMF0107, have a similar morphology to S. racemosum, but each display distinct phenotypic and genotypic features. The polyphasic approach, combining the results of complementary phenotypic and genomic assays, was instrumental in describing and characterising these two new Syncephalastrum species.

There is increased concern that the quality, generalizability, and reproducibility of biomedical research can be influenced by the sex of animals used. We studied the differences between male and female mice in response to invasive pulmonary mucormycosis including susceptibility to infection, host immune reaction, and responses to antifungal therapy. We used diabetic ketoacidotic (DKA) or neutropenic mice infected with either Rhizopus delemar or Mucor circinelloides. The only difference detected was that when DKA mice were infected with M. circinelloides, female mice were more resistant to infection than male mice (median survival time of 5 vs. 2 days for female and male mice, respectively). However, a 100% lethality was detected among infected animals of both sexes. Treatment with either liposomal amphotericin B (L-AMB) or posaconazole (POSA) protected mice from infection and eliminated the difference seen between infected but untreated female and male mice. Treatment with L-AMB consistently outperformed POSA in prolonging survival and reducing tissue fungal burden of DKA and neutropenic mice infected with R. delemar or M. circinelloides, in both mouse sexes. Although little difference was detected in cytokine levels among both sexes, mucormycosis infection in the DKA mouse model induced more inflammatory cytokines/chemokines involved in neutrophil (CXCL1) and macrophage (CXCL2) recruitment vs. uninfected mice. As expected, this inflammatory response was reduced in the neutropenic mouse model. Our studies show that there are few differences between female and male DKA or neutropenic mice infected with mucormycosis with no effect on the outcome of treatment or host immune response.

Mucormycoses are rare but serious opportunistic fungal infections caused by filamentous organisms of the order Mucorales. Here we report the first molecular identification of Rhizopus oryzae (heterotypic synonym Rhizopus arrhizus), R. delemar, and Apophysomyces ossiformis as the etiological agents of three cases of severe mucormycosis in Honduras. Conventional microbiological cultures were carried out, and DNA was extracted from both clinical samples and axenic cultures. The ITS ribosomal region was amplified and sequenced. Molecular tools are suitable strategies for diagnosing and identifying Mucorales in tissues and cultures, especially in middle-income countries lacking routine diagnostic strategies.

Background: Mucormycosis is a worldwide angio-invasive fungal infection that is associated with high morbidity and mortality. A few European studies have focused on the epidemiology. Methodology: A retrospective longitudinal descriptive study was performed with inpatients diagnosed with mucormycosis (ICD-9-CM, code 117.7, cases 1997-2015; and ICD-10, code B46, cases 2016-2018; along with length of hospital stay) in Spanish public hospitals between 1 January 1997 and 31 December 2018. Data were obtained from the Minimum Basic Data Set (CMBD in Spanish). Principal findings: A total of 962 patients were recorded; 665 were men. The mean age (±SD) was 55±18.8 years. The annual incidence rate increased from 0.74 to 1.24 cases per million person-years. The lethality rate was 31.3%. Renal failure (41.6%) and hematological malignancy (36.3%) were the main factors involved. Conclusions: Mucormycosis is a rare infectious disease in Spain, but it has had a significantly increased incidence in the last two decades. Being an adult male and having diabetes, neoplasm or renal failure are the main factors associated. High mortality is usually associated mainly with hematological malignancy and renal failure. CMBD studies could be an efficient tool for assessing changes in the epidemiology of mucormycosis.

Mucolares are an ancient group of fungi encompassing the causal agents for the lethal infection mucormycosis. The high lethality rates, the emerging character of this disease, and the broad antifungal resistance of its causal agents are mucormycosis features alarming clinicians and researchers. Thus, the research field around mucormycosis is currently focused on finding specific weaknesses and targets in Mucorales for developing new treatments against mucormycosis. In this work, we tested the role of the white-collar genes family in the virulence potential of Mucor lusitanicus. In this regard, the study of the role in virulence of the three genes of this family, mcwc-1a, mcwc-1b, and mcwc-1c, resulted in a marked functional specialization, as only mcwc-1a was essential to maintain the virulence potential of M. lusitanicus. The traditional role of wc-1 genes regulating light-dependent responses is a thoroughly studied field, whereas their role in virulence remains uncharacterized. In this work, we investigated the mechanism involving mcwc-1a in virulence from an integrated transcriptomic and functional approach during the host-pathogen interaction. Our results revealed mcwc-1a as a master regulator controlling an extensive gene-network. Further dissection of this gene-network clustering its components by type of regulation and functional criteria disclosed a multifunctional mechanism depending on diverse pathways. In the absence of phagocytic cells, mcwc-1a controlled pathways related to cell motility and cytoskeleton that could be associated with the essential tropism during tissue invasion. After phagocytosis, several oxidative responding pathways dependent on mcwc-1a were activated during the germination of M. lusitanicus spore inside of phagocytic cells, which is the first stage of the infection. The third relevant group of genes involved in virulence and regulated by mcwc-1a belonged to the “unknown function,” indicating that new and hidden pathways are involved in virulence. The unknown function category is especially pertinent in the study of mucormycosis, as it is highly enriched in specific fungal genes that represent the most promising targets for developing new antifungal compounds. These results essentially unveil a complex multifunctional mechanism used by wc-1 genes to regulate the pathogenic potential in Mucorales that could also apply to other fungal pathogens.

Cultural recovery of Mucorales from hyphae-laden tissue is poor, and the clinical implications of culture positivity are scarcely studied. Therefore, we compared clinical and histological characteristics of culture-positive and culture-negative histology-proven pulmonary mucormycosis cases among cancer patients. Histology specimens were blindly reviewed by a Thoracic Pathologist and graded on four histopathologic features: hyphal quantity, tissue necrosis, tissue invasion, and vascular invasion. Twenty cases with a corresponding fungal culture were identified; five were culture-positive, and 15 culture-negative. Although no statistically significant differences were found, culture-positive patients were more likely to exhibit a high burden of necrosis and have a high burden of hyphae but tended to have less vascular invasion than culture-negative patients. In terms of clinical characteristics, culture-positive patients were more likely to have acute myeloid leukemia (60% vs. 27%, p=0.19), a history of hematopoietic cell transplant (80% vs. 53%, p=0.31), severe lymphopenia (absolute lymphocyte count ≤500/µL, 100% vs. 73%, p=0.36), and monocytopenia (absolute monocyte count ≤100/µL, 60% vs. 20%, p=0.11). Forty-two-day all-cause mortality was comparable between culture-positive and culture-negative patients (60% and 53%, p=0.80). This pilot study represents the first comprehensive histopathological scoring method to examine the relationship between histopathologic features, culture positivity, and clinical features of pulmonary mucormycosis.

Mucormycosis is an opportunistic fungal infection that is increasingly affecting patients with Coronavirus Disease (COVID-19). This connection is particularly pronounced in specific populations, including individuals with diabetes or those who have recently undergone corticosteroid therapy. Additionally, Cytomegalovirus (CMV) infection is a frequent complication among COVID-19 patients who have previously received corticosteroid or other immune-modulatory treatments. In this case report, we present the clinical details of a 56-year-old male who developed post-COVID pneumonia complicated by both cutaneous mucormycosis and CMV infection.

The epigenetic modifications control the pathogenicity of human pathogenic fungi, which have been poorly studied in Mucorales; causative agents of mucormycosis. This order belongs to a group referred to as early-diverging fungi that are characterized by high levels of N6-methyldeoxyadenine (6mA) in their genome with dense 6mA clusters associated with actively expressed genes. AlkB enzymes can act as demethylases of 6mA in DNA, with the most remarkable eukaryotic examples being mammalian ALKBH1 and Caenorhabditis elegans NMAD-1. Mucor lusitanicus (formerly M. circinelloides f. lusitanicus) genome contains one gene, dmt1, and two genes, dmt2 and dmt3, encoding proteins homologs to C. elegans NMAD-1 and ALKBH1, respectively. The function of the three genes was analyzed by the generation of single and double deletion mutants for each gene. Multiple processes were studied in the mutants, but defects were only found in single and double deletion mutants for dmt1. In contrast to the wild-type strain, dmt1 mutants showed an increase of 6mA levels during the dimorphic transition, suggesting that 6mA regulates dimorphism in M. lusitanicus. Furthermore, the spores of dmt1 mutants challenged with macrophages underwent a reduction of polar growth, suggesting that 6mA also has a role during the spore-macrophage interaction that could be important in the infection process.

Mucormycosis (previously called zygomycosis or phycomycosis), an aggressive, life-threatening infection is further aggravating the human health-impact of the devastating COVID-19 pandemic. Additionally, a great deal of mostly misleading discussion is focused also on the aggravation of the COVID-19 accrued impacts due to the white and yellow fungal diseases. In addition to the knowledge of important risk factors, modes of spread, pathogenesis and host defences, a critical discussion on the botanical insights into the main causative agents of mucormycosis in the current context is very imperative. Given above, in this paper: (i) general background of the mucormycosis and COVID-19 is briefly presented; (ii) overview of fungi is presented, the major beneficial and harmful fungi are highlighted; and also the major ways of fungal infections such as mycosis, mycotoxicosis, and mycetismus are enlightened; (iii) the major causative agents of mucormycosis are critically discussed; (iv) the systematic position, occurrence, structure, and the major modes of reproduction are summarized for Rhizopus sp. and Mucor sp., the major causative agents of mucormycosis; (v) the other causative agents of mucormycosis includes Cunninghamella bertholletiae, Apophysomyces elegans, Lichtheimia (Absidia), Saksenaea, and Rhizomucor pusillus are briefly introduced; (vi) facts related with the infection-misnomers based on fungi colour are also highlighted; and lastly, (vii) the major take-home message and clues for future research on the subject are listed.

Mucormycosis is a lethal disease caused by Mucorales, which are emerging as human pathogens with virulent behavior. Antifungal resistance and ineffective treatments are two major causes that explain the high mortality for this disease. Consequently, the research community is searching for virulence determinants that could be repurposed as targets to develop new treatments against mucormycosis. Our work explores an RNA interference (RNAi)-based approach to find targets involved in the virulence of Mucorales. A transcriptome-wide analysis compared sRNAs and their target mRNAs in two Mucor lusitanicus different pathotypes, virulent and avirulent, generating a list of 75 loci selected by their differential sRNA accumulation in these strains. As a proof of concept and validity, an experimental approach characterized two loci showing opposite behavior, confirming that RNAi activity causes their differential expression in the two pathotypes. We generated deletion mutants for two loci and a knockin-strain overexpressing for one these loci. Their functional analysis in murine virulence assays identified the gene wex1, a putative DEDDy exonuclease with RNase domains, as an essential factor for virulence. The identification of wex1 showed the potential of our approach to discover virulence factors not only in Mucorales but also in any other fungal model with an active RNAi machinery. But, more importantly, it adds a new layer to the biological processes controlled by RNAi in M. lusitanicus, confirming that the Dicer-dependent RNAi pathway can silence gene expression to promote virulence.

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 de-scribing 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 Argonautes proteins. Conversely, NCRIP relies on RNA-dependent RNA Polymerases and an atypical ribonuclease III (RNaseIII). 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.