Fusarium oxysporum - Toxic Black Mould

fusarium toxic black mould

Another type fungus commonly referred to as toxic mould is Fusarium oxysporum which is a ubiquitous soil inhabitant. It has the ability to exist as saprophytes, and degrade lignin and complex carbohydrates - associated with soil debris. They are pervasive plant endophytes that can colonize plant roots. These species are associated with roots and lower stems of a variety of fresh vegetables, including lettuce and other greens as well as stored tubers and corms. It has been recently shown to denitrify and produce nitrogen in a way that is similar to some bacteria. In plants F. oxysporum causes a condition called Fusarium wilt, which is lethal to plants and swift - by the time a plant shows any outward sign of infection, it is already too late, and the plant will die.It is normally found in tap water as well as in essentially all fresh plant material, including vegetables.

Fusarium has worldwide distribution and is mainly know as a plant pathogen. When favourable conditions exist it can colonise indoor environment especially places with high humidity or freely available water such as cooling units and air-conditioning systems.

The host range of these fungi is extremely broad, and includes animals, ranging from arthropods to humans as well as plants. Fusarium oxysporum and Fusarium solani are greatly feared as opportunistic fungi in hospitals’ bone marrow transplant wards, where imnunocompromised patiens are undergoing therapies. Fusarium toxic mould have emerged as the second most frequent fungal pathogens, after Aspergillus, in high-risk patients with haematological malignancies, recipients of solid organ and allogeneic bone marrow, or stem cell transplants. This species represent a serious hazard to neutropenic patients.

In immunologically competent hosts Fusarium black mould  infections are relatively rare involving mainly skin around surgical wounds, burns, deep ulcers, nails, or cornea. Less commonly, these organisms have been documented as aetiological agents in localized tissue infections, including septic arthritis, endophthalmitis, cystitis, peritonitis, and brain abscesses.

Probably nobody normally goes through a day without ingesting a significant quantity of these fungi.

In humans Fusarium toxic mould and its mycotoxins is causing the diseases Fungal keratitis, Onychomycosis, and Hyalohyphomycosis. Fusarium produces a range of mycotoxins from which the main ones belong to the group of fumonisins and trichothecenes. Fumonisins are know to be hepatoxic?, neurotoxic?, nephrotoxic? and carcinogenic?.

Other Fusarium species

The genus currently contains over 20 species, of which Fusarium solani is the most frequent human pathogen. Other medically relevant species are F. moniliforme and less commonly, F. anthophilum, F. chlamydosporum, F. dimerum, F. equiseti, F. lichenicola, F. napi forme, F. proliferatum, F. Semitecum, and F. verticilloides.

Fusarium toxic spores

fusarium black mould spores

Fusarium oxysporum spores have characteristic easily recognisable shape. Fusarium produced two types of conidia, one is small and is call microconidium and the other type is large and is called macroconidium. The micro-conidia are usually spherical or elongated, slightly curved, mostly unicellular, hyaline, 3-15 x 3-5 μm in size. These small spores are produced by microphialides, swollen at the base and pointed at the tip. Macroconidia are falcate, usually three-septate, 20-35 x 3-5 μm in size.

Fusarium black mould conidia are relatively small and are rare in the indoor environment. They can contaminate virtually any surface and cause range of infection. Fusarium conidia are distributed by wind, splashing water or the movement of spores by contact (hands, clothing, gloves, etc). Fusarium will survive in diseased plant tissue or on wall surfaces for many months and conidia will also survive extended periods of time until suitable condition for sporulation occur. They can be frequently found in accumulated dust, plant pots, greenhouse walls, benches, floors etc.