The term fungus refers to a wide range of life forms that grow on both
living and dead organic materials. Mushrooms, yeasts and molds are three large
classes of fungi. Fungi are essential players in ecosystems, participating in
the recycling of dead organic matter.
As infecting parasites, fungi can be hostile to other living creatures--
plants and animals, large and small. Humans use fungi in food production and are
hosts to resident species such as candida. Fungi produce disease in different
ways. The most obvious are skin infections that everyone develops. Surface
infections of the scalp produce itching and scaling (dandruff) and are a
life-long feature of most humans. Invasive fungal infections can be
life-threatening and are more difficult to diagnose and treat than bacterial
Some fungi exist in the environment and are able to cause an invasive
infection in otherwise healthy individuals. Other fungi are opportunistic fungi
that become invasive when immune defenses are compromised. Humans are hosts to
resident species such as candida that are more a nuisance to people with normal
immune systems, but become life threatening infectious agents when immune
defense is compromised.
Diagnosis of fungal infection is difficult. There are many problems when you try to connect a test result to a disease.
Fungi are so abundant and there are so many varieties in every environment that
it is seldom easy to pick just one cause among many. Fungi are inhaled and
ingested. Foods always contain fungal spores and even actively growing molds.
Skin tests using fungal antigens are routine in allergy practice. Skin
prick tests and serum IgE tests are performed with inhalant and food allergens,
molds and yeasts. These tests reveal immediate hypersensitivity, but delayed
hypersensitivity to fungi is more important in the production of diseases,
especially chronic lung disease. There are no easy, reliable tests.
Molds reproduce by releasing spores into the air. Mold spores are usually
more abundant than plant pollens. Molds grow mycelia, branching thread-like
structures that infiltrate materials. Spore bearing structures, conidiophores,
grow from mycelia. The main route of entry of mold spores is through inhalation
of dust particles contaminated with the fungi.
Immune responses to inhaled spores is a natural defense against infection.
The immune response, however, can induce inflammation in the lungs and lead to
chronic disease if the exposure continues. Inhaled spores of pathogenic fungi
sometimes grow in lungs and other organs, establishing chronic and sometimes
lethal infections that are difficult to diagnose. There is an overlap of
allergic hypersensitivity diseases and infection.
Fungi produce toxins that are released into the air. Büngeret al studied
five toxigenic airborne moulds of the genera Aspergillus and Penicillium
collected at composting plants: sterigmatocystin, fumagillin, verruculogen,
penitrem A, and roquefortine C. All five extracts caused toxic effects to
cultured cells. They suggested that mycotoxins may be involved in producing the
lung diseases from the inhalation of organic dust. Panaccione and Coyle
reported finding ergot alkaloids associated with Aspergillus fumigatus. Ergot
molds produce an array of potent chemicals. The hallucinogen, LSD, was derived
from ergot alkaloids.
See Politics of Mold