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ALTERNARIA
Mould
The U.S. Government’s
Occupational Safety and Health Administration [OSHA] lists the
following as the health effects of Alternaria mould:
Allergen, Irritant, Hypersensitivity
Pneumonitis, Dermatitis.
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Taxonomic
Classifications
Kingdom: Fungi
Phylum: Ascomycota
Class: Euascomycetes
Order: Pleosporales
Family: Pleosporaceae
Genus: Alternaria |
Toxic Mould Species:
Mould Pictures
Absidia Mould
Alternaria Mould
Aspergillus Mould
Aureobasidium Mould
Blastomyces Mould
Candida Mould
Coccidioides
Cryptococcus Mould
Curvularia Mould
Histoplasma Mould
Mucor Mould
Penicillium Mould
Pseudallescheria
Sporothrix Mould
Stachybotrys Mould
Verticillium Mould
Yeast |
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brown hyphae and conidia
mature conidia have transverse and longitudinal divisions septate
hyphae
vtpb-www.cvm.tamu.edu/vtpb/vet_micro/
charts_fungi/fungi/alternaria.html
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The dark
brown spores are borne in simple or branched chains from the tips of
simple dark conidiophores and are divided into several cells by
transverse and vertical walls. New spores are produced by the
extrusion of wall material through a pore at the tip of the previous
spore. Commonly isolated from decaying plant materials; also causing
plant diseases. Spores of Alternaria species are dispersed by air currents and are usually a
major component of outdoor air. Holomorphs: Clathrospora,
Leptosphaeria, Pleospora, Pyrenophora. Refs: Ellis
1971, 1976; Joly 1964. |
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Above mould photos and captions are courtesy of:
www.botany.utoronto.ca/ResearchLabs/MallochLab/
Malloch/Moulds/Alternaria.html |
Description and Natural Habitats
Alternaria mould is a cosmopolitan dematiaceous (phaeoid) fungus
commonly isolated from plants, soil, food, and indoor air environment. The
production of melanin-like pigment is one of its major characteristics. Its teleomorphic genera are called Clathrospora and Leptosphaeria.
The large spore size 20 - 200 microns in length and 7 - 18 microns in sizes,
suggests that the spores from this fungi will deposited in the nose, mouth
and upper respiratory tract.
Specimens of Alternaria are
often found growing on carpets, textiles and horizontal surfaces such as
window frames. It is commonly found in soil, seeds and plants. It is known
to be a common allergen. It appears as a velvety tuft with long soft hairs
and its color ranges from dark olive green to brown. Alternaria is a dry
spore and is readily found in air samples as well as on tape lift samples.
Alternaria is commonly found in water damaged buildings, and a significant
increase in its numbers compared to outdoor levels can be a sign of growth.
Commonly found in outdoor air,
on many kinds of plants and food products and prefers rotting farmland
manure. It may be resistant to fungicides. Alternaria is considered an
occasional contaminant of water damaged building materials which contain
cellulose. Although Alternaria is a notable source of fungal allergy,
pathogenic infections are also reported infrequently.
Species
The genus Alternaria currently contains around 50 species. Among
these, Alternaria alternata is the most common one isolated from
human infections. Some authorities suggest that Alternaria alternata
is a representative species complex rather than a single species and
consists of several heterogenous species. While Alternaria chartarum,
Alternaria dianthicola, Alternaria geophilia, Alternaria
infectoria, Alternaria stemphyloides, and Alternaria
teunissima are among the other Alternaria spp. isolated from
infections, some Alternaria strains reported as causative agents
remain unspecified. Health Effects
Among the species of alternaria, the
species Alternaria alternata is capable of producing tenuazonic acid and
other toxic metabolites which may be associated with disease in humans or
animals. Alternaria produces large spores having sizes between 20 - 200
microns in length and 7 - 18 microns in width, suggesing that the spores
from this fungi are deposited in the nose, mouth, and upper respiratory
tract. It may be related to
bakers asthma. It has been associated with
hypersensitivity pneumonitis, sinusitis, deratomycosis, onychomycosis,
subcutaneous phaeohyphomycosis, and invasive infection. Common cause of
extrinsic asthma (immediate-type hypersensitivity: type I). Acute symptoms
include edema and bronchiospasms, chronic cases may develop pulmonary
emphysema. Further explanations about the health disease caused by
alternaria species shown below:
1. onychomycosis - Fungal
Infection of the nails is known as "onychomycosis". It is increasingly
common with increased age. It rarely affects children.
2. subcutaneous phaeohyphomycosis - Subcutaneous infections
occur worldwide, usually following the traumatic implantation of fungal
elements from contaminated soil, thorns or wood splinters. Exophiala
jeanselmei and Wangiella dermatitidisare the most common agents
and cystic lesions occur most often in adults. Occasionally, overlying
verrucous lesions are formed, especially in the immunosuppressed patient.
Subcutaneous phaeohyphomycosis
caused by Exophiala jeanselmei |
Subcutaneous phaeohyphomycosis
caused by Wangiella dermatitidis. |
Macroscopic
Features
Alternaria
mould grow rapidly and the colony size reaches a diameter of 3 to 9 cm
following incubation at 25°C for 7 days on potato glucose agar. The
colony is flat, downy to woolly and is covered by grayish, short, aerial
hyphae in time. The surface is greyish white at the beginning which later
darkens and becomes greenish black or olive brown with a light border. The
reverse side is typically brown to black due to pigment production.
Microscopic
Features
Alternaria mould have septate, brown
hyphae. Conidiophores are also septate and brown in color, occasionally
producing a zigzag appearance. They bear simple or branched large conidia
(7-10 x 23-34 µm) which have both transverse and longitudinal septations.
These conidia may be observed singly or in acropetal chains and may
produce germ tubes. They are ovoid to obclavate, darkly pigmented,
muriform, smooth or roughened. The end of the conidium nearest the
conidiophore is round while it tapers towards the apex. This gives the
typical beak or club-like appearance of the conidia.
Laboratory
Precautions
No
special precautions other than general laboratory precautions are
required.
Susceptibility
In vitro susceptibility
testing for phaeoid fungi is not standardized yet. The in vitro activity
of some novel antifungal drugs has so far been investigated. While
caspofungin
was shown to be active in vitro against Alternaria,
voriconazole
also appeared promising and generated lower MICs than
itraconazole
for Alternaria strains .
Amphotericin
B and
flucytosine
therapy may achieve successful clinical outcome in phaehyphomycosis.
Treatment with
fluconazole,
itraconazole, or
terbinafine
may also be effective. However, further data are required to clarify their
actual place in treatment of Alternaria infections.
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