Cryptic species inStachybotrys chartarum

Brain abscess caused by Scedosporium boydii in a systemic lupus erythematosus patient: A case report and literature review

Scedosporium boydii is considered as emerging opportunists affecting both immunocompromised and immunocompetent individuals. Diagnosis and treatment of Scedosporium infections can be challenging, and the outcome is frequently fatal, especially in patients with disseminated infections. Metagenomic next-generation sequencing (mNGS) is a promising adjunctive diagnostic approach for uncommon pathogens. Here, we report a rare case of brain abscess caused by S. boydii in a systemic lupus erythematosus (SLE) patient. This case highlights the importance of mNGS in the early diagnosis of S. boydii. Additionally, the combined application of culture and molecular tools may be promising in the clinical diagnosis of fungal disease.

Thyridium revised: Synonymisation of Phialemoniopsis under Thyridium and establishment of a new order, Thyridiales

The genus Thyridium, previously known as a saprobic or hemibiotrophic ascomycete on various plants, was revised taxonomically and phylogenetically. Sequences of the following six regions, that is, the nuclear ribosomal internal transcribed spacer (ITS) region, the large subunit (LSU) of rDNA, the second largest RNA polymerase II subunit (rpb2) gene, translation elongation factor 1-alpha (tef1) gene, the actin (act) gene, and the beta-tubulin (tub2) gene, were generated for molecular phylogenetic analyses of species of this genus. Phialemoniopsis, a genus encompassing medically important species, is synonymised with Thyridium based on molecular evidence and morphological similarities in their asexual characters. The generic concept for Thyridium is expanded to include species possessing both coelomycetous and hyphomycetous complex asexual morphs. In addition to type species of Thyridium, T.vestitum, nine species were accepted in Thyridium upon morphological comparison and molecular phylogenetic analyses in this study. All seven species of Phialemoniopsis were treated as members of the genus Thyridium and new combinations were proposed. A bambusicolous fungus, Pleosporapunctulata, was transferred to Thyridium, and an epitype is designated for this species. A new species, T.flavostromatum, was described from Phyllostachyspubescens. The family Phialemoniopsidaceae, proposed as a familial placement for Phialemoniopsis, was regarded as a synonym of Thyridiaceae. A new order, Thyridiales, was established to accommodate Thyridiaceae; it forms a well-supported, monophyletic clade in Sordariomycetes.

Hepatic phaeohyphomycosis due to a novel dematiaceous fungus, Pleurostoma hongkongense sp. nov., and importance of antifungal susceptibility testing

Pleurostoma species are wood-inhabiting fungi and emerging opportunistic pathogens causing phaeohyphomycosis. In this study, we isolated a dematiaceous fungus, HKU44T, from the subhepatic abscess pus and drain fluids of a liver transplant recipient with post-transplant biliary and hepatico-jejunostomy bypass strictures. Histology of the abscess wall biopsy showed abundant fungal hyphae. The patient survived after a second liver transplant and antifungal therapy. On SDA, HKU44T grew initially as white powdery colonies which turned beige upon maturation. Hyphae were septate and hyaline. Phialides were monophialidic and laterally located, generally closely associated to a cluster of conidia which were usually reniform. Phylogenetic analyses showed that HKU44T is most closely related to, but distinct from, Pleurostoma ootheca and Pleurostoma repens. These suggested that HKU44T is a novel Pleurostoma species, for which the name Pleurostoma hongkongense sp. nov. is proposed. Antifungal susceptibility testing showed that Pleurostoma species possessed high MICs/MECs for fluconazole, 5-flucytosine and the echinocandins; whereas they exhibited a high strain-to-strain variability to the susceptibilities to the other triazoles. As for amphotericin B, ∼65% of the Pleurostoma strains had low MICs (≤1 µg/mL). DNA sequencing should be performed to accurately identify fungi with Pleurostoma/Phialophora-like morphologies, so is antifungal susceptibility testing for patients with Pleurostoma infections.

Truncated satratoxin gene clusters in selected isolates of the atranone chemotype of Stachybotrys chartarum (Ehrenb.) S. Hughes

The fungus Stachybotrys (S.) chartarum was isolated from culinary herbs, damp building materials, and improperly stored animal forage. Two distinct chemotypes of the fungus were described that produced either high-cytotoxic macrocyclic trichothecenes (S type) or low-cytotoxic atranones (A type). Recently, two distinct gene clusters were described that were found to be necessary for the biosynthesis of either macrocyclic trichothecenes (21 SAT (Satratoxin) genes) or atranones (14 ATR (Atranone) genes). In the current study, PCR primers were designed to detect SAT and ATR genes in 19 S. chartarum chemotype S and eight S. chartarum chemotype A strains. Our analysis revealed the existence of three different genotypes: satratoxin-producing strains that harbored all SAT genes but lacked the ATR gene cluster (genotype S), non-satratoxin-producing strains that possessed the ATR genes but lacked SAT genes (genotype A), and a hitherto undescribed hybrid genotype among non-satratoxin-producing strains that harbored all ATR genes and an incomplete set of SAT genes (genotype H). In order to improve the discrimination of genotypes, a triplex PCR assay was developed and applied for the analysis of S. chartarum and S. chlorohalonata cultures. The results show that genes for macrocyclic trichothecenes and atranones are not mutually exclusive in S. chartarum. Correlation of the new genotype-based concept with mycotoxin production data shows also that macrocyclic trichothecenes are exclusively produced by S. chartarum genotype S strains.

Analysis of Pyricularia oryzae and P. grisea from Different Hosts Based on Multilocus Phylogeny and Pathogenicity Associated with Host Preference in China

Pyricularia oryzae and P. grisea are important agents of major diseases on a wide range of gramineous hosts. Whereas P. oryzae is the most important pathogen causing outbreaks of rice blast, P. grisea is mainly a pathogen of crabgrass. In this study, 103 P. oryzae and 20 P. grisea isolates were collected from seven species of plants, and we analyzed their phylogeny, pathogenicity, and relationship with host preferences to investigate the differences among them from different hosts. Based on phylogenetic analysis of multilocus sequences, 16 isolates from crabgrass and four isolates from green bristlegrass were identified as P. grisea and another 103 isolates from crabgrass, green bristlegrass, goose grass, foxtail millet, wild millet, rice, and sedge belonged to P. oryzae. Results of pathogenicity tests by artificial inoculation demonstrated that six of 10 P. oryzae isolates from rice and three of 44 P. oryzae isolates from green bristlegrass showed cross-infectivity on green bristlegrass and rice, respectively. Taken together, our results demonstrated that isolates from green bristlegrass and crabgrass consist of both P. oryzae and P. grisea and that P. oryzae isolates showed cross-infectivity between rice and green bristlegrass, suggesting that host shifts may occur for P. oryzae and P. grisea.

Genera Acremonium and Sarocladium Cause Brown Spot on Bagged Apple Fruit in China

Apple fruit spot disease has caused serious economic losses for years in China since the widespread application of fruit bagging in production. Although the three genera Trichothecium, Alternaria, and Acremonium have been reported to be the causal agents, studies on the disease etiology and pathogen biology are still sparse. Here, we report characterization of eight fungal isolates from lesions on 126 symptomatic fruit samples collected in Shaanxi Province, China. Pathogenicity of the isolates was assessed. DNA sequences were obtained at four loci, including D1/D2 domains of the large-subunit nrRNA gene, internal transcribed spacer regions 1 and 2, 5.8S nrDAN gene, a fragment of the actin gene, and a fragment of the β-tubulin. Based on phylogenetic analysis and morphological features, three new species were found: Acremonium mali, Sarocladium liquanensis, and Sarocladium mali. In addition, we made the first report of Sarocladium terricola as a plant pathogen. Temperature and moisture significantly affected in vitro conidial germination of five Acremonium-like species, and their impact on infection of apple fruit was tested using Acremonium sclerotigenum. Conidia of five species germinated from 15 to 35°C in free water; four of the species had optimum temperature around 25°C, whereas conidia of S. terricola had an optimum temperature of 30°C. Conidial germination rate increased as relative humidity (RH) increased. The five isolates had relatively high conidial germination rates at RH > 97%, with a significant decline at 95% RH. Incidence of infection also increased in proportion to RH. In free water, conidial germination was relatively unaffected by temperature.

Infections caused by Scedosporium/Lomentospora species: Clinical and microbiological findings in 21 cases

The clinical and microbiological characteristics of infections caused by Scedosporium/ Lomentospora species in 21 patients are described. We searched retrospectively the records for Scedosporium/ Lomentospora species seen at the University Hospital Virgen de las Nieves from 2006 to 2017. Out of them, 16 were male; mean age at diagnosis was 57.8 (±SD 15) years; all patients had risk factors for fungal infection such as corticosteroids and/or immunosuppressive treatment in 18 (85.7%) patients, pulmonary diseases in seven (33.3%) cases, hematological malignancies in six (28.5%), and organ transplantation in three (14.2%) patients. Most patients had infection in the lung/pleura (17/80.9%); cough was present in 12 patients and dyspnea in another 12, and the mean interval until diagnosis was 13.6 days. The most frequent species was S. apiospermum/S. boydii in 14 patients (66.6%), followed by L. prolificans in seven. The diagnosis was obtained from sputum in 12 (57.1%) cases, followed by pleural fluid and bronchoalveolar lavage in two of each. The most frequently used antifungals were voriconazole and amphotericin B, but combination of more than one antifungal drug was only used in three patients. Ten patients were cured, and six patients died as a consequence of the infection; three patients had chronic infection. In general, infections caused by Scedosporium/Lomentospora species are rare, serious, and difficult to diagnose and treat, having a high index or mortality especially in those caused by L. prolificans.

Molecular Identification and Susceptibility Testing of Molds Isolated in a Prospective Surveillance of Triazole Resistance in Spain (FILPOP2 Study)

Antifungal resistance is increasing by the emergence of intrinsically resistant species and by the development of secondary resistance in susceptible species. A previous study performed in Spain revealed levels of azole resistance in molds of between 10 and 12.7%, but secondary resistance in Aspergillus fumigatus was not detected. We used itraconazole (ITZ)-supplemented medium to select resistant strains. A total of 500 plates supplemented with 2 mg/liter of ITZ were sent to 10 Spanish tertiary hospitals, and molecular identification and antifungal susceptibility testing were performed. In addition, the cyp51A gene in those A. fumigatus strains showing azole resistance was sequenced. A total of 493 isolates were included in the study. Sixteen strains were isolated from patients with an infection classified as proven, 104 were isolated from patients with an infection classified as probable, and 373 were isolated from patients with an infection classified as colonization. Aspergillus was the most frequent genus isolated, at 80.3%, followed by Scedosporium-Lomentospora (7.9%), Penicillium-Talaromyces (4.5%), Fusarium (2.6%), and the order Mucorales (1%). Antifungal resistance was detected in Scedosporium-Lomentospora species, Fusarium, Talaromyces, and Mucorales Three strains of A. fumigatus sensu stricto were resistant to azoles; two of them harbored the TR₃₄+L98H mechanism of resistance, and the other one had no mutations in cyp51A The level of azole resistance in A. fumigatus remains low, but cryptic species represent over 10% of the isolates and have a broader but overall higher range of antifungal resistance.

Fungal Diversity Revisited: 2.2 to 3.8 Million Species

The question of how many species of Fungi there are has occasioned much speculation, with figures mostly posited from around half a million to 10 million, and in one extreme case even a sizable portion of the spectacular number of 1 trillion. Here we examine new evidence from various sources to derive an updated estimate of global fungal diversity. The rates and patterns in the description of new species from the 1750s show no sign of approaching an asymptote and even accelerated in the 2010s after the advent of molecular approaches to species delimitation. Species recognition studies of (semi-)cryptic species hidden in morpho-species complexes suggest a weighted average ratio of about an order of magnitude for the number of species recognized after and before such studies. New evidence also comes from extrapolations of plant:fungus ratios, with information now being generated from environmental sequence studies, including comparisons of molecular and fieldwork data from the same sites. We further draw attention to undescribed species awaiting discovery in biodiversity hot spots in the tropics, little-explored habitats (such as lichen-inhabiting fungi), and material in collections awaiting study. We conclude that the commonly cited estimate of 1.5 million species is conservative and that the actual range is properly estimated at 2.2 to 3.8 million. With 120,000 currently accepted species, it appears that at best just 8%, and in the worst case scenario just 3%, are named so far. Improved estimates hinge particularly on reliable statistical and phylogenetic approaches to analyze the rapidly increasing amount of environmental sequence data.

Molecular and phenotypic descriptions of Stachybotrys chlorohalonata sp. nov. and two chemotypes of Stachybotrys chartarum found in water-damaged buildings

Twenty-five Stachybotrys isolates from two previous studies have been examined and compared, using morphological, chemical and phylogenetic methods. The results show that S. chartarum sensu lato can be segregated into two chemotypes and one new species. The new species, S. chlorohalonata, differs morphologically from S. chartarum by having smooth conidia, being more restricted in growth and producing a green extracellular pigment on the medium CYA. S. chlorohalonata and S. chartarum also have different tri5, chs1 and tub1 gene fragment sequences. The two chemotypes of S. chartarum, chemotype S and chemotype A, have similar morphology but differ in production of metabolites. Chemotype S produces macrocyclic trichothecenes, satratoxins and roridins, while chemotype A produces atranones and dolabellanes. There is no difference between the two chemotypes in the tub1 gene fragment, but there is a one nucleotide difference in each of the tri5 and the chs1 gene fragments.

Less-frequent Fusarium species of clinical interest: correlation between morphological and molecular identification and antifungal susceptibility

Forty-eight Fusarium isolates morphologically identified as belonging to seven species of clinical interest (i.e., Fusarium chlamydosporum, Fusarium dimerum, Fusarium incarnatum, Fusarium napiforme, Fusarium nygamai, Fusarium proliferatum, and Fusarium sacchari) were characterized molecularly by the analysis of the sequences of the TUB region of the beta-tubulin gene. F. chlamydosporum and F. dimerum were the most genetically heterogeneous species. A high degree of correlation between the morphological and molecular identification was shown among the isolates studied. A table with the key morphological features for the identification of these Fusarium species is provided. The antifungal susceptibilities of the Fusarium isolates to 11 antifungal drugs were tested; terbinafine was the most active drug against all the species tested with the exception of F. incarnatum, for which amphotericin B was the most active.

Pseudallescheria fusoidea, a new cause of osteomyelitis

Osteomyelitis resulting from a mold infection often presents as a chronic and indolent disease process. Described here for the first time is a case of osteomyelitis of the foot caused by the mold Pseudallescheria fusoidea, which resulted from traumatic implantation after an injury sustained 3 years earlier.

In vitro antifungal susceptibility and molecular characterization of clinical isolates of Fusarium verticillioides (F. moniliforme) and Fusarium thapsinum

A microdilution method was used to test 11 antifungal drugs against clinical isolates of Fusarium thapsinum and three different phylogenetic clades of Fusarium verticillioides that were characterized by sequencing a region of the beta-tubulin gene. Terbinafine was the most-active drug against both species, followed by posaconazole against F. verticillioides.

Intra-specific and intra-sporocarp ITS variation of ectomycorrhizal fungi as assessed by rDNA sequencing of sporocarps and pooled ectomycorrhizal roots from a Quercus woodland

The Internal Transcribed Spacer (ITS) regions of ribosomal DNA are widely used as markers for phylogenetic analyses and environmental sampling from a variety of organisms including fungi, plants, and animals. In theory, concerted evolution homogenizes multicopy genes so that little or no variation exists within populations or individuals. However, contrary to theory, ITS variation has been confirmed in populations and individuals from a diverse range of eukaryotes. The presence of intraspecific and intra-individual variation in multicopy genes has important implications for ecological and phylogenetic studies, yet relatively little is known about natural variation of these genes, particularly at the community level. In this study, we examined intraspecific and intra-sporocarp ITS variation by DNA sequencing from sporocarps and pooled roots from 68 species of ectomycorrhizal fungi collected at a single site in a Quercus woodland. We detected ITS variation in 27 species, roughly 40% of the taxa examined. Although intraspecific ITS variation was generally low (0.16-2.85%, mean = 0.74%), it was widespread within this fungal community. We detected ITS variation in both sporocarps and ectomycorrhizal roots, and variation was present within species of Ascomycota and Basidiomycota, two distantly related lineages within the Fungi. We discuss the implications of such widespread ITS variability with special reference to DNA-based environmental sampling from diverse fungal communities.

Universal in vitro antifungal resistance of genetic clades of the Fusarium solani species complex

Eleven antifungal drugs were tested against representative isolates of the four phylogenetic clades of the Fusarium solani species complex obtained in a multilocus sequence analysis. They all showed very poor activity, with no differences among the clades. Amphotericin B was the most active drug.

PCR-RFLP of ITS rDNA for the rapid identification of Penicillium subgenus Biverticillium species

RFLP of ITS rDNA is proposed as a useful tool for molecular identification of the most common species of biverticillate penicillia. 60 isolates were analysed representing 13 species and 21 unique sequences were produced. The combination of five restriction enzymes was successful in separating 12 species. However, the variety Penicillium purpurogenum var. rubrisclerotium remained indistinguishable from Penicillium funiculosum. P. funiculosum appeared as the most confused species, being mis-identified with Penicillium miniolutum and Penicillium pinophilum, which were originally part of the species, and with P. purpurogenum perhaps because of the common production of red pigment. Penicillium variabile was difficult to investigate as introns were found on half of the isolates. Penicillium piceum, Penicillium rugulosum, Penicillium loliense, Penicillium erythromellis and P. purpurogenum were homogeneous from molecular and morphological positions and corresponded to a well circumscribed taxon. Furthermore, intraspecific variability was evidenced within P. pinophilum and P. funiculosum. The ex-type isolate of P. funiculosum produced a unique pattern. The method is sensitive, rapid and inexpensive and can be used for isolate identification of the biverticillate species. It is recommended particularly when many isolates have to be authentificated prior to analysis for phylogenetic assessment or population genetics.

Amplified Fragment Length Polymorphism Analysis and Internal Transcribed Spacer and coxII Sequences Reveal a Species Boundary Within Pythium irregulare

ABSTRACT Pythium irregulare is a plant-pathogenic oomycete that causes significant damage to a variety of crops, including ornamentals and vegetables. Morphological as well as molecular studies have reported high levels of genetic diversity within P. irregulare sensu lato which has raised the question as to whether it is a single species or is actually a complex of morphologically similar (cryptic) species. In this study, we used amplified fragment length polymorphism (AFLP) fingerprinting and DNA sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal genes (ITS region) and a portion of the mitochondrial cytochrome oxidase II gene and the spacer region between coxI and coxII to characterize 68 isolates of P. irregulare from the United States. The ITS sequence of a P. irregulare neotype at the CBS collection as well as ITS and coxII sequences for P. irregulare, P. spinosum, and P. sylvaticum from previous studies were included in our analysis. Cluster analysis identified a 19-isolate group (IR-II) that separated itself from the rest of the sample (IR-I). Population structure and sequence analyses supported the distinction of IR-I and IR-II and identified IR-II as P. irregulare sensu stricto. IR-I was designated Pythium sp. clade IR-I. Two insertion/deletion mutations and nine nucleotide substitutions in the ITS region and three in the sequence of coxII and the adjacent spacer region separated the two species. Additionally, they differed significantly (P > 0.01) in the frequency of 182 (77%) AFLP alleles. Gene flow results suggested that P. irregulare sensu stricto and Pythium sp. clade IR-I are cryptic species capable of exchanging favorable alleles (Nm = 0.72).

Molecular phylogeny of the Pseudallescheria boydii species complex: proposal of two new species

Pseudallescheria boydii (anamorph Scedosporium apiospermum) is the species responsible for human scedosporiosis, a fungal infection with a high mortality rate and which is difficult to treat. Recently, it has been demonstrated that high genetic variation exists within this species. We have performed a morphological and molecular study involving numerous strains of clinical or environmental origins and from different countries. The analysis of partial sequences of the beta-tubulin (two loci) and calmodulin genes and the internal transcribed spacer region of the rRNA gene has demonstrated that P. boydii is a species complex. The combined analysis of the sequences of the four loci of 60 strains has showed the presence of 44 haplotypes in the in group. Three species morphologically related to P. boydii sensu stricto, i.e., Pseudallescheria angusta, Pseudallescheria ellipsoidea, and Pseudallescheria fusoidea, which had previously been considered synonyms, could be differentiated genetically from P. boydii in our study. It is relevant that two of the three strains now included in P. ellipsoidea have caused invasive infections. The species Pseudallescheria minutispora and Scedosporium aurantiacum are clearly phylogenetically separated from the other species studied and are here proposed as new. Morphological features support this proposal. All the strains included in S. aurantiacum species have a clinical origin, while those included in P. minutispora are environmental. Further studies are needed to demonstrate whether all the species included in the P. boydii complex have different clinical spectra and antifungal susceptibility.

Taxonomic history and current status of Stachybotrys chartarum and related species

The fungus Stachybotrys chartarum is the type species of the genus Stachybotrys. It is a cellulolytic saprophyte with a worldwide distribution and is frequently recovered in water-damaged buildings. Three isolates of S. chartarum were studied morphologically from single-spore isolations. Significant differences were found with the sizes, lengths, width, and L/W ratio of conidia and phialides among the isolates. QPCR analysis on S. chartarum, S. yunnanensis, S. chlorohalonata, S. elegans, S. microspora, and S. nephrospora showed that the primers and probe for detecting S. chartarum used by commercial laboratories were not able to differentiate S. chartarum from S. chlorohalonata and S. yunnanensis. Results suggested that S. chartarum may not be well delineated even after S. chlorohalonata was recently segregated from the species complex. Further study on the taxonomic status of the epithet S. chartarum is necessary.

PRACTICAL IMPLICATIONS

Six species of Stachybotrys are present indoors. Differentiation of Stachybotrys chartarum from S. chlorohalonata, and S. yunnanensis can be challenging using either morphological or QPCR methods. Caution should be taken to identify S. chartarum and closely related species and to explain their health effects implication for indoor air quality investigations.

Evolutionary studies of ectomycorrhizal fungi: recent advances and future directions

The three biggest advances in fungal molecular phylogenetics in the last few years have been (1) the huge expansion in data sets, (2) the development of nonribosomal loci for phylogenetic analysis, and (3) the use of increasingly sophisticated types of analyses. In addition, advances in parallel computing hold great promise for dramatic increases in speed of analysis. These changes have had, or will have, a direct impact on mycorrhizal ecology through the use of sequence-based identification and an indirect impact through the conclusions drawn from such studies. One problem in the field has been the accidental addition of erroneous sequences to the public databases through a variety of means, including polymerase change reaction contamination. We discuss several examples, suggest ways to identify errors, and argue the case for third-party annotations of sequences. Multiple studies have produced compelling evidence that the ectomycorrhizal habit has developed convergently in multiple lineages of fungi and plants. We reexamine the case for loss of the ectomycorrhizal habit in fungi and show that the results are model dependent.Key words: internal transcribed spacer (ITS) region, peroxidase genes, likelihood models, erroneous data, ectomycorrhizal habit.

Stachybotrys chartarum: a fungus for our time

Stachybotrys chartarum, a fungus found in damp buildings and sometimes ascribed a role in building-related illnesses, produces a variety of secondary metabolites including trichothecenes, triprenylated phenolics, and a new class of diterpenoids called atranones. A related fungus, Memnoniella echinata also produces trichothecenes and the triprenylated phenolics. Herein the production of these compounds from cultures of the above are reviewed.

A geographically diverse set of isolates indicates two phylogenetic lineages withinStachybotrys chartarum

Stachybotrys chartarum is a black mitosporic fungus capable of dense colonization of cellulose-based building materials such as drywall. The presence of S. chartarum in indoor environments has been reported as linked to a variety of alleged environment-related illnesses including infant acute idiopathic pulmonary hemorrhage, although there continues to be insufficient (especially exposure) data to support such associations. We investigated genetic variation among 52 morphologically and geographically diverse, indoor and outdoor isolates of S. chartarum sensu lato using molecular markers based on β-tubulin, calmodulin, elongation factor-1 alpha, and trichodiene synthase genes, as well as the internal transcribed spacer region of nuclear ribosomal DNA. Gene genealogies proved concordant in dividing all isolates into two strongly supported clades. The majority of the variable sites separating these lineages were fixed within each of these clades, and there was no evidence of recombination between genotypes. The results of this study therefore provide strong support for the recognition of two phylogenetic species within S. chartarum sensu lato, and further demonstrate the limitations of morphological characters in delineating monophyletic taxa among morphologically simple fungi.Key words: Stachybotrys atra, cryptic speciation, calmodulin, elongation factor-1 alpha, trichodiene synthase.