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Acremonium Species
The
U.S. Government's Occupational
Safety and Health Administration [OSHA]
lists
the following as the health effects of Acremonium mold:
Allergen,
Irritant, Hypersensitivity pneumonitis, Dermatitis. Taxonomic Classification
Description and Natural Habitats Acremonium species. are filamentous, cosmopolitan fungi commonly isolated from plant debris and soil. The sexual state of Acremonium is not well-defined. Thus, it is classified among the deuteromycetes group of fungi by some authorities. Others prefer to include it in Ascomycota phylum, due to its structural properties similar to those of this group. According to The Environmental Reporter, Vol. 3, No. 9, “Acremonium species is primarily isolated from soil, plant debris, foodstuffs, hay, rotting mushrooms, and indoor building materials, such as the acoustic and thermal fiber glass insulation used in heating ventilation and air conditioning system. Acremonium has a high water affinity of Aw 0.90-0.98 and is often isolated from cooling coils, drain pans, window seals, and water from humidifiers. Additionally, Acremonium is occasionally found growing with Stachybotrys. The spores of this fungus are formed in a slimy mass resulting to a limited aerosolization.”
Species
The genus Acremonium currently contains 100 species, of
which most are saprophytic, being isolated from dead plant material and
soil.
There are three
main species of Acremonium implicated in infections: Acremonium
falciforme, Acremonium kiliense, and Acremonium recifei.
Pathogenicity and Clinical Significance Acremonium is considered as one of the causative agents of white grain mycetoma. In addition to some cases of onychomycosis due to Acremonium, cases of endocarditis, endophthalmitis, keratitis, meningitis, and peritonitis have also been reported. This fungus is known to cause opportunistic infections mainly among the immunocompromised patients, such as bone marrow transplant recipients.
Acremonium species are encountered as contaminants as well thus; their isolation in culture requires careful evaluation. Additionally, some Acremonium species are even parasitic toward other fungal organisms which are generally termed as mycoparasites.
Macroscopic Features Ø Growth rate is moderately rapid and colonies are compact, flat or folded and occasionally raised in the center; initially, texture is glabrous, velvety and membrane – like and becoming cottony with age due to the overgrowth of loose hyphae; Ø Colonies are observed having diameter measuring from 1 to 3 cm after seven days of incubation at 25°C; and Ø Surface colony color ranges from white, to pale gray or pale pink while the reverse is uncolored or a pink to rose colored - pigmentation may be observed.
Microscopic FeaturesØ Hyphae are hyaline and septate which are characteristically fine and narrow; Ø Phialides are erect, unbranched and solitary which arise directly from the hyphal tips; phialides are separated by a septum from the hyphae and taper towards their tips; and Ø Conidia are hyaline, may be unicellular or multicellular, fusiform – shaped with a slight curve or may look like a shallow crescent, appear in clusters, in balls or as fragile chains rarely, with size of 2 – 3 x 4 – 8 µm, and are found at the tips of the phialides; the structural properties of the conidia may vary depending on the species.
Table 1. Structural Differences of Conidia of Acremonium species
“The wet conidial spores are disseminated mechanically by insects or water droplets. Occasionally, spores from old growth are wind disseminated,” according to The Environmental Reporter, Vol. 3, No. 9
Mold Analysis On spore traps, Acremonium is not easily identified due to their very small, colorless and non – distinctive spores. Furthermore, some spores are so small that they may be obscured by background debris. Air sampling cultures are a better way to recover and identify airborne Acremonium spores. Acremonium can easily be identified on direct examination as it is possible to view distinctive chains or the slimy heads of conidia.
Laboratory
Precautions
Susceptibility Reported data on in vitro susceptibility are very limited. The novel azoles, posaconazole and voriconazole show favorable in vitro activity against Acremonium strains.
On the other hand, in vivo response largely depends on both antifungal therapy and surgical involvement. Amphotericin B remains as the mainstay of therapy among the available antifungal agents. |
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