PATHOGENICITY:  Commonly considered a contaminant. Stachybotrys alternans produces a potenttoxin that is lethal to animals eating contaminated forage. Inhalation or percutaneous absorption has caused mild symptoms in humans.

RATE OF GROWTH:  Rapidly matures within 4 days. However, it takes a constant moisture content in a wall for 10 to 12 days before it starts to germinate.

COLONY MORPHOLOGY:  Hyphae are septate and colorless to dark. Conidiophores are simple or branched, many become pigmented and rough with age and bares clusters of 3-10 phialides. The phialides are colorless or pigmented, nonseptate and cylindrical with a swollen upper portion. Conidia are dark, oval (average 4.5 x 9 um) single celled and smooth or rough walled and usually form in clusters.

Stachybotrys chartarum (a.k.a. Stachybotrys atra) is a ubiquitous saprophytic fungus (obtains its food by digesting organic matter) which can produce mycotoxins of the trichothecene and spirolactone families. Various strains of Stachy may differ greatly in their ability to produce mycotoxin substances.

The trichothecene mycotoxins are potent protein synthesis inhibitors and cause immunosuppresion in laboratory animals. In experimental animals studies, the trichothecenes affect rapidly proliferating tissues such as skin and mucosa, as well as lymphatic and hematopoietic tissues that regenerate from undifferentiated germinal cells (Ueno). Mycotoxins in the trichothene family appear to bind to receptors on the cell membrane, decrease both RNA and DNA production and interfere with protein synthesis by blocking the initiation of translation. In laboratory animals, acute exposure to large amounts of trichothecene toxins resulting in a rapid release of stored white blood cells into circulation, while repeated or chronic exposure destroys granulocytic precursor cells in bone marrow leading to white cell depletion. Among the reported cellular effects are: mitogen B/T lymphocyte blastogenesis suppression, decrease of IgM, IgG, IgA; impaired macrophage activity and migration-chemotaxis; broad immunosuppressive effects on the cellular and humoral-mediated immune response leading to secondary infections; immunomodulation leading to spontaneous antibody increase and immunosuppressive effects in human peripheral blood lymphocytes.

Toxigenic strains of Stachy may also produce spirolactones (stachybotrylactone) and spirolactams (stachybotrylactam) toxins which produce anticomplement effects. Possible synergistic effects between the trichothecenes and these mycotoxins have not yet been evaluated.

Positive skin reactions to the fungus have also been found in some asthmatics living or working in Stachybotrys contaminated rooms, suggesting a hypersensitivity component in addition to the potential for Mycotoxicosis. Thus the fungal spores themselves or chemicals carried on the spores may produce either allergic or toxigenic effects.

If Stachy spores are released into the air, there is a potential for humans to develop symptoms such as coughing, wheezing, runny nose, irritated eyes or throat, skin rash, and diarrhea. There are a few reports in the scientific literature of improvement of symptoms when people left an area where Stachy or other molds were found, or after moldy materials were removed from a dwelling or workplace.

It is theorized that the above symptoms may result from an allergic response to the Stachy, or from toxins produced by Stachy, or from another environmental agent. However, it is difficult to show that these types of symptoms are due to Stachy for several reasons:
        1) When buildings are sampled, usually several other molds are found in addition to Stachy, and these molds
            could also cause symptoms;
        2) These symptoms are vary nonspecific and can be related to other allergens such as dust mites, animal hair and
            dander, pollen, etc., or to infectious agents such as bacteria (which produce an element called endotoxins) or viruses;
        3) Currently, research has not clarified what level of Stachy is necessary to produce symptoms;

A task group of the World Health Organization (WHO) concluded that "an association between trichothecenes and human disease is possible, however only limited data is available thus conclusive evidence in humans has not yet been shown".