Alternaria - Toxic Black Mould

alternaria black mould

Alternaria is a cosmopolitan dematiaceous (phaeoid)? fungus commonly isolated from plants, soil, food, and indoor air environment. It has been isolated from floor dust, carpet and mattress dust; less common on damp walls, gypsum board and wallpaper. Alternaria is known to cause of soft rot and blue stain of wet joinery. It has also been isolated from UFFI, window putty, (acrylic latex) paint, humidifier water, textiles, hay, cereals and fruit. For Alternaria, the minimum RH needed for growth was reported as 85%.

Alternaria colonizes the surface of leaves, stems and other plant organs, so it is often referred to as phylloplane? fungus. There is large number of species in this genus, they are a natural part of fungal flora. They are normal agents of decay and decomposition. Alternaria can be pathogenic to various fruits and vegetables.

The spores are airborne and found in the soil and water, as well as indoors and on objects. The club-shaped spores are single or form long chains. They can grow thick colonies which are usually green, black, or gray.

alternaria black mould spores

Alternaria alternata, a fungus which is relatively common in proliferations on water-damaged wallboard, wallpaper and other indoor substrates substantially consisting of finely divided cellulose.

The genus Alternaria currently contains around 50 species. Among these, Alternaria alternata is the most common one isolated from human infections. Under suitable conditions, some of these species produce a range of mycotoxins and other metabolites. Alternaria alternata is the most important mycotoxin-producing species.

Alternaria spores are relatively characteristic because of their size, shape, and septation. Its spores are large, light brown to brown, smooth or rough, multiple-celled with transverse and frequently longitudinal septation.

Alternaria and health

Many human health disorders can be caused by various Alternaria species. Alternaria mainly attacks skin and mucous membranes, including on the eyeballs and causes disorders within the respiratory tract. At least 20 species of Alternaria are known to synthesise toxic metabolites, but their natural occurrence is not considered relevant.

Alternaria allergies are common, but serious infections are rare, except in people with compromised immune systems.
Strains of Alternaria alternata produce a chemically diverse group of mycotoxins including alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TEA), altenuene (ALT) and altertoxins (AT). Toxicity tests with the individual mycotoxins indicate that alternariol and alternariol monomethyl ether are not very acutely toxic, but are mutagenic . Altertoxins and related perylene derivatives are acutely toxin and potent mutagens. Tenuazonic acid is not mutagenic in bacterial assays, but is toxic to several animal species such as dogs and chickens. Tenuazonic acid has indirectly been associated with the human hematological disorder known as Onyalay. At present, there are no regulatory limits for Alternaria toxins in foods.

The major allergenic fraction of Alternaria alternata is heterogeneous and can induce allergenic reactions at very low concentrations in sensitized individuals. Investigators have identified 32 antigens and 19 different allergens. Alt 1, heat-stable acidic glycoprotein,  is considered to be the major allergen.

Various health disorders in humans and animals caused by Alternaria moulds are commonly refered to as alternariosis and alternariatoxicosis.  Alternaria moulds have been implicated in allergic rhinitis and mycotic sinusitis  whether invasive or allergic.

Alternaria inhalation under laboratory controlled conditions produced acute bron-chospasm  and sensitization. Alternaria is considered to be a risk factor for respiratory arrest in asthma.
Spores of Alternaria alternata are often cited as evidence of sensitization to the fungus and links to the presence, persistence, and severity of asthma.

Alternaria species are recognized causative agents of mycotic keratitis and phaeohyphomycosis. Clinical manifestations include cutaneous infections, paranasal sinusitis, osteomyelitis and peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD).

In immunocompetent patients, Alternaria colonizes the paranasal sinuses, leading to chronic hypertrophic sinusitis. In immunocompromised patients the colonization may end up with development of invasive disease. It is among the causative agents of otitis media in agricultural field workers.

Also Alternaria alternata is the most common pathogenic species other species from these genus such as Alternaria dianthicola, Alternaria geophilia, Alternaria infectoria, Alternaria stemphyloides, and Alternaria teunissima  occur frequently.