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Chaetomium perlucidum
Chaetomium perlucidum is a neurotropic[3] dematiaceous (melanated cell wall)[4] fungus that is naturally found in the soil,[5] including in agricultural soil,[6] and in the stems of dead plants.[7] The fungus can also be found on the feathers of birds, manure, seeds, and even paper.[3] It is able to thrive at temperatures of 35 and 42 °C (95 and 108 °F).[3] The fungus is an invasive opportunist[3][4] to humans that can cause diseases such as onychomycosis (fungus on nails), otolaryngologic (head and neck) or respiratory inflammations (like sinusitis, pneumonia, and empyema), and brain necrosis.[3] HistoryIt was first formally recorded in 1956 in Ukraine by K. S. Sergeeva.[1][8] MorphologyChaetomium perlucidum is pigmented and dark in colour, appearing hairy and wooly, with a growth rate of 4-5 mm/day.[3] Perithecia (fruiting body)Chaetomium perlucidum's fruiting bodies become fully mature in 13-16 days.[3] The fruiting body's structural width is 90-200 μm, with an ostiolar pore (open pore) width of 30-50 μm.[3] Setae (bristle / "hair" structures)Setae width is 2-3 μm and can have lengths of up to 700 μm.[3] The setae are unbranched and appear to undulate.[3] Mature ascosporesFully mature ascospores are 12.5-14 μm x 6-7.5 μm in size.[3] They are smooth, oval-shaped, and brown in colour.[3] Lipid / fatty acid compositionChaetomium perlucidum is composed of saturated, monounsaturated, and polyunsaturated fatty acids.
PathogenicityThe fungus can cause chronic fungal infections in humans.[3][10] An infection can spread throughout the body from a single point of infection into various other systems, e.g., the central nervous, cardiovascular, respiratory, and immune systems, with especially a low prognosis for cerebral infections.[3] Mode of transmission and infectionInfections take hold in the brain and progress to spread throughout the body.[3] Pathways of entry into the host's body include via cutaneous lesions, oral intake, or intravenously.[3] SusceptibilityThere have been at least two reported cases of cerebral phaeohyphomycosis in humans with one case resulting in death, reported in 2003.[3] Both cases occurred in immunosuppressed individuals already suffering from complications of other unrelated diseases.[3] Recreational drug users, or patients who have undergone intravenous or transplant procedures at even hospitals are also susceptible to being infected by C. perlucidum.[3] Treatment and prognosisMost Chaetomium fungal diseases are without known cure[3] and in one case of death from 1996, antifungal therapy through administering Amphotericin B (AMB) proved ineffective.[11] AMB is a common and leading antibiotic treatment prescribed for fungal infections.[12] In one case, C. perlucidum infection in the brain caused death from hemorrhaging throughout the body (especially in the brain) and complications that arose from acute inflammation.[3] However, the physical removal of a C. perlucidum growth through a lobectomy (surgically removing the fungal growth from an area of affected organ/s) was successful in curing another patient from infection.[3] Culturing techniquesChaetomium perlucidum ascospores can be cultured and grown in the lab through incubation on potato flake agar at 25°C for 6-10 days.[3] Optimal growth temperature however is at 37°C.[3] Mature perithecia can be obtained if the fungus has access to a sterile plant source.[3] Occurrence in farming soilChaetomium perlucidum was found more frequently in tilled than in untilled farmland.[13] References
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