First Case of Invasive Stachybotrys Sinusitis

A Chemically Defined Medium That Supports Mycotoxin Production by Stachybotrys chartarum Enabled Analysis of the Impact of Nitrogen and Carbon Sources on the Biosynthesis of Macrocyclic Trichothecenes and Stachybotrylactam

Stachybotrys chartarum (Hypocreales, Ascomycota) is a toxigenic fungus that is frequently isolated from water-damaged buildings or improperly stored feed. The secondary metabolites formed by this mold have been associated with health problems in humans and animals. Several authors have studied the influence of environmental conditions on the production of mycotoxins, but these studies focused on undefined or complex substrates, such as building materials and media that impeded investigations of the influence of specific nutrients. In this study, a chemically defined cultivation medium was used to investigate the impact of several nitrogen and carbon sources on growth of S. chartarum and its production of macrocyclic trichothecenes (MTs) and stachybotrylactam (STLAC). Increasing concentrations of sodium nitrate were found to positively affect mycelial growth, the level of sporulation, and MT production, while ammonium nitrate and ammonium chloride had an inhibitory effect. Potato starch was the superior and most reliable carbon source tested. Additionally, we observed that the level of sporulation was correlated with the production of MTs but not with that of STLAC. In this study, we provide a chemically well-defined cultivation medium suitable for standardized in vitro testing of the capacity of S. chartarum isolates to produce macrocyclic trichothecenes. IMPORTANCE Macrocyclic trichothecenes (MTs) are highly toxic secondary metabolites that are produced by certain Stachybotrys chartarum strains, which consequently pose a risk for animals and humans. To identify hazardous, toxin-producing strains by analytical means, it is important to grow them under conditions that support MT production. Nutrients determine growth and development and thus the synthesis of secondary metabolites. Complex rich media are commonly used for diagnostics, but batch differences of supplements pose a risk for inconsistent data. We have established a chemically defined medium for S. chartarum and used it to analyze the impact of nitrogen and carbon sources. A key finding is that nitrate stimulates MT production, whereas ammonium suppresses it. Defining nutrients that support MT production will enable a more reliable identification of hazardous S. chartarum isolates. The new medium will also be instrumental in analyzing the biosynthetic pathways and regulatory mechanisms that control mycotoxin production in S. chartarum.

Production of Satratoxin G and H Is Tightly Linked to Sporulation in Stachybotrys chartarum

Stachybotrys chartarum is a toxigenic fungus that is frequently isolated from damp building materials or improperly stored forage. Macrocyclic trichothecenes and in particular satratoxins are the most potent mycotoxins known to be produced by this fungus. Exposure of humans or animals to these secondary metabolites can be associated with severe health problems. To assess the pathogenic potential of S. chartarum isolates, it is essential to cultivate them under conditions that reliably promote toxin production. Potato dextrose agar (PDA) was reported to be the optimal nutrition medium for satratoxin production. In this study, the growth of S. chartarum genotype S strains on PDA from two manufacturers led to divergent results, namely, well-grown and sporulating cultures with high satratoxin concentrations (20.8 ± 0.4 µg/cm²) versus cultures with sparse sporulation and low satratoxin production (0.3 ± 0.1 µg/cm²). This finding is important for any attempt to identify toxigenic S. chartarum isolates. Further experiments performed with the two media provided strong evidence for a link between satratoxin production and sporulation. A comparison of three-point and one-point cultures grown on the two types of PDA, furthermore, demonstrated an inter-colony communication that influences both sporulation and mycotoxin production of S. chartarum genotype S strains.

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?