Rapid and selective detection of macrocyclic trichothecene producing Stachybotrys chartarum strains by loop-mediated isothermal amplification (LAMP)

Development and Application of Loop-Mediated Isothermal Amplification (LAMP) Assays for Rapid Diagnosis of the Bat White-Nose Disease Fungus Pseudogymnoascus destructans

Pseudogymnoascus destructans (= Geomyces destructans) is a psychrophilic filamentous fungus that causes White-Nose Disease (WND; the disease associated with White-Nose Syndrome, WNS) in hibernating bats. The disease has caused considerable reductions in bat populations in the USA and Canada since 2006. Identification and detection of the pathogen in pure cultures and environmental samples is routinely based on qPCR or PCR after DNA isolation and purification. Rapid and specific direct detection of the fungus in the field would strongly improve prompt surveillance, and support control measures. Based on the genes coding for ATP citrate lyase1 (acl1) and the 28S-18S ribosomal RNA intergenic spacer (IGS) in P. destructans, two independent LAMP assays were developed for the rapid and sensitive diagnosis of the fungus. Both assays could discriminate P. destructans from 159 tested species of filamentous fungi and yeasts. Sensitivity of the assays was 2.1 picogram per reaction (pg/rxn) and 21 femtogram per reaction (fg/rxn) for the acl1 and IGS based assays, respectively. Moreover, both assays also work with spores and mycelia of P. destructans that are directly added to the master mix without prior DNA extraction. For field-diagnostics, we developed and tested a field-applicable version of the IGS-based LAMP assay. Lastly, we also developed a protocol for preparation of fungal spores and mycelia from swabs and tape liftings of contaminated surfaces or infected bats. This protocol in combination with the highly sensitive IGS-based LAMP-assay enabled sensitive detection of P. destructans from various sources.

Mycobiota and mycotoxin-producing fungi in southern California: their colonisation and in vitro interactions

Fungal contamination in water-damaged houses has become a major concern because of their potential health effects. During our survey in 100 water-damaged houses in southern California, we have reported 42 outdoor and 14 indoor fungal species throughout the year. Six commonly occurring indoor fungal species are Alternaria alternata, Aspergillus niger, Chaetomium globosum, Cladosporium herbarum, Penicillium chrysogenum and Stachybotrys chartarum. In the damp building materials, S. chartarum was found to be associated with A. niger, C. globosum and P. chrysogenum but not with A. alternata and C. herbarum. Stachybotrys chartarum showed strong antagonistic effect against A. alternata and C. herbarum and significantly inhibited in vitro growth of A. alternata and C. herbarum but had no effect on A. niger, C. globosum and P. chrysogenum. Two trichothecenes, produced by Stachybotrys sp., trichodermin and trichodermol, significantly inhibited spore germination and in vitro growth of A. alternata and C. herbarum but had no effect on A. niger, C. globosum, P. chrysogenum and S. chartarum. In the damp building materials (drywall, ceiling tile, and oak wood), S. chartarum significantly inhibited the growth of A. alternata and C. herbarum and had no effect on A. niger, C. globosum and P. chrysogenum in these substrata.

Asymmetric stem-loop–mediated isothermal amplification of nucleic acids for DNA diagnostic assays by simple modification of canonical PCR primers

Nucleic acid–based assays have been adopted as mainstream tools for clinical diagnostics, food safety, and environment monitoring with the merits of accuracy, rapidity, and sensitivity. Loop-mediated isothermal amplification (LAMP) is a well-established method to rapidly identify nucleic acids and has gained recognition and been developed for clinical applications in resource-limited areas. However, the needs for specifically designed primer sets and non-specific amplification hinder the development of LAMP-based nucleic acid tests. Here, a promoted method, termed asymmetric stem-loop–mediated isothermal amplification (ASLAMP) by simple modification of canonical PCR primers, was developed to attempt to overcome those drawbacks. The two primers in the ASLAMP reaction can be easily obtained by adding a stem-loop sequence part to one PCR primer at 5′-ends to get the folding primer (FP), then adding the same primer to the counter canonical PCR primer at 5′-ends to get the turn-back primer (TP). The ASLAMP method was demonstrated in detecting the H1N1 gene fragment with merits of simple primer design, short target sequence, and high amplification efficiency. In addition, the ASLAMP method showed similar efficacy compared with LAMP targeting at the same H1N1 gene sequence. Furthermore, Shigella detection monitored by real-time fluorescence and endpoint colorimetric approaches were taken as examples for evaluation of the practical application of the ASLAMP method, both offered 100% sensitivity and specificity. In conclusion, the novel ASLAMP method with simplicity of primer design, low requirement of equipment, efficiency, and rapidity has exhibited its great prospect for establishment of DNA isothermal amplification in point of care application.

Stachybotrys chartarum-A Hidden Treasure: Secondary Metabolites, Bioactivities, and Biotechnological Relevance

Fungi are renowned as a fountainhead of bio-metabolites that could be employed for producing novel therapeutic agents, as well as enzymes with wide biotechnological and industrial applications. Stachybotrys chartarum (black mold) (Stachybotriaceae) is a toxigenic fungus that is commonly found in damp environments. This fungus has the capacity to produce various classes of bio-metabolites with unrivaled structural features, including cyclosporins, cochlioquinones, atranones, trichothecenes, dolabellanes, phenylspirodrimanes, xanthones, and isoindoline and chromene derivatives. Moreover, it is a source of various enzymes that could have variable biotechnological and industrial relevance. The current review highlights the formerly published data on S. chartarum, including its metabolites and their bioactivities, as well as industrial and biotechnological relevance dated from 1973 to the beginning of 2022. In this work, 215 metabolites have been listed and 138 references have been cited.

The Evolution of the Satratoxin and Atranone Gene Clusters of Stachybotrys chartarum

Stachybotrys chartarum is frequently isolated from damp building materials or improperly stored animal forage. Human and animal exposure to the secondary metabolites of this mold is linked to severe health effects. The mutually exclusive production of either satratoxins or atranones defines the chemotypes A and S. Based upon the genes (satratoxin cluster, SC1-3, sat or atranone cluster, AC1, atr) that are supposed to be essential for satratoxin and atranone production, S. chartarum can furthermore be divided into three genotypes: the S-type possessing all sat- but no atr-genes, the A-type lacking the sat- but harboring all atr-genes, and the H-type having only certain sat- and all atr-genes. We analyzed the above-mentioned gene clusters and their flanking regions to shed light on the evolutionary relationship. Furthermore, we performed a deep re-sequencing and LC-MS/MS (Liquid chromatography–mass spectrometry) analysis. We propose a first model for the evolution of the S. chartarum genotypes. We assume that genotype H represents the most ancient form. A loss of the AC1 and the concomitant acquisition of the SC2 led to the emergence of the genotype S. According to our model, the genotype H also developed towards genotype A, a process that was accompanied by a loss of SC1 and SC3.

Update on Stachybotrys chartarum-Black Mold Perceived as Toxigenic and Potentially Pathogenic to Humans

In nature, there are many species of fungi known to produce various mycotoxins, allergens and volatile organic compounds (VOCs), as well as the commonly known etiological agents of various types of mycoses. So far, none of them have provoked so much emotion among homeowners, builders, conservators, mycologists and clinicians as Stachybotrys chartarum. This species compared to fungi of the genera Fusarium and Aspergillus is not as frequently described to be a micromycete that is toxigenic and hazardous to human and animal health, but interest in it has been growing consistently for three decades. Depending on the authors of any given review article, attention is focused either on the clinical aspects alongside the role of this fungus in deterioration of biomaterials, or aspects related to its biology, ecology and taxonomic position. On the one hand, it is well established that inhalation of conidia, containing the highest concentrations of toxic metabolites, may cause serious damage to the mammalian lung, particularly with repeated exposure. On the other hand, we can find articles in which authors demonstrate that S. chartarum conidia can germinate and form hyphae in lungs but are not able to establish an effective infection. Finally, we can find case reports that suggest that S. chartarum infection is linked with acute pulmonary hemorrhage, based on fungal structures recovered from patient lung tissue. New scientific reports have verified the current state of knowledge and note that clinical significance of this fungus is exceedingly controversial. For these reasons, understanding S. chartarum requires reviewing the well-known toxigenic features and harmful factors associated with this fungus, by gathering the newest ones into a coherent whole. The research problem related to this fungus seems to be not overly publicized, and there is still a demand to truthfully define the real threats of S. chartarum and phylogenetically related species. The most important problem, which should be fully elucidated as soon as possible, remains the clarification of the pathogenicity of S. chartarum and related species. Maybe it is urgent time to ask a critical question, namely what exactly do we know 28 years after the outbreak of pulmonary hemorrhage in infants in Cleveland, Ohio, USA most likely caused by S. chartarum?

Detection of Stachybotrys chartarum isolates from faba beans dust during threshing

Stachybotrys (S.) chartarum had been related to dangerous health problems in animals and humans that take place when exposure to S. chartarum toxins. S. chartarum had been isolated from various substrates, ranging from inappropriately stored feed and culinary herbs to damp buildings. To evaluate the pathogenic potential of isolates, it is essential to identify them with different methods. The occurrence and genetic diversity of S. chartarum isolates from faba beans dust during threshing in Upper Egypt were investigated. Low counts of Stachybotrys were found (six isolates) and identified morphologically by single-spore isolation and molecularly by the amplification of the specific internal transcribed spacer (ITS) region and glyceraldehydes-3-phosphate dehydrogenase (gpd). The genetic diversity of the collected isolates was studied by specific genes random primer polymerase chain reaction (SGRP-PCR). The phylogenetic analysis of S. chartarum showed that the specific primers IT51 and StacR3 used by commercial laboratories for detecting S. chartarum were not able to differentiate species of S. chartarum from S. chlorohalonata and unweighted pair group method of arithmetic averages (UPGMA) cluster analysis of SGRP fragments confirmed this result. The six isolates of S. chartarum were analyzed for the presence of trichodiene synthase (Tri5) gene, which needed in the early stage of the trichothecene synthesis path. All the tested isolates were positive for the Tri5 gene. Further study on the taxonomic status of the epithet S. chartarum is necessary and presence of sub species to S. chartarum might be acceptable depending on the variations of morphological characteristics which were confirmed by molecular techniques.