Chaetomium atrobrunneum

Chaetomium atrobrunneum is a darkly pigmented mould affiliated with the fungal division, Ascomycota.[1][2][3] This species is predominantly saprotrophic,[2] although it has been known to infect animals including humans, showing a proclivity for the tissues of the central nervous system.[4][5] Chaetomium atrobrunneum was described in 1949 from a mouldy military mattress cover obtained from the island of Guadalcanal.[6]

Chaetomium atrobrunneum
Scientific classification
Kingdom:
Fungi
Division:
Ascomycota
Subdivision:
Pezizomycotina
Class:
Sordariomycetes
Order:
Sordariales
Genus:
Chaetomium
Species:
C. atrobrunneum
Binomial name
Chaetomium atrobrunneum
Ames (1949)
Synonyms
  • Chaetomium fusisporale J.N. Rai & Mukerji (1962)
  • Chaetomium rectopilium Fergus & Amelung (1971)

Growth and morphology

Chaetomium atrobrunneum is a darkly pigmented, predominantly mycelial fungus.[2] Colonies of C. atrobrunneum typically are dark grey to black in colour with a woolly appearance.[1] It forms sexual fruiting structures called perithecia that are spherical to oval in shape,[7] measuring between 70–150 µm in width when fully matured at 10 days.[1] The perithecia are covered sparsely with straight, finely-blistered, dark brown hairs that become occasionally become broadly branched with age.[1][3] The perithecia contain asci within which are 8 ascospores that spindle-shaped, have a single sub-apical germ pore and are brown to grey in colour,[1][3] although a mutant with colourless ascospores has been reported.[8] The ascospores of this species are smooth-walled and measure 9–11 µm in length by 4.5–6 µm in width.[1][3]

Ecology and physiology

Chaetomium atrobrunneum has been reported from rabbit dung,[7] milled Italian rice,[9] water-damaged building materials, concrete, plaster and wallpaper.[10] Chaetomium atrobrunneum grows more slowly at 25 °C (77 °F) than most other species of the genus,[1][3] reaching a colony diameter of 16–21 mm after 7 days incubation on Cornmeal Agar (CMA).[11] By contrast, its growth at higher temperatures is much more rapid than many other Chaetomium species, producing colonies of approximately 41–44 mm in diameter after 7 days incubation at 42 °C (108 °F) on CMA.[3][11] Chaetomium atrobrunneum is distinct from other Chaetomium species by its smaller perithecia, its ability to grow at relatively high temperatures,[3] and the occasional presence in this taxon of perithecial hairs that branch at wide angles.[6]

Chaetomium atrobrunneum is strongly cellulolytic,[12] and cellulose-containing growth media can be used to selectively cultivate this and other Chaetomium species.[13] This species has also been reported to produce chaetoatrosin A, a selective inhibitor of chitin synthase II. This enzyme is involved in septum formation and cellular division,[14] and its inhibition by chaetoatrosin A is thought to be the mechanism underlying the antifungal effects of C. atrobrunneum culture filtrates against several medically important fungi including Cryptococcus neoformans.[14]

Pathogenicity

Chaetomium atrobrunneum is a rare pathogen of humans that tends to infect the tissues of the central nervous system.[1] Its pathogenicity is thought to be supported by its ability to grow at high temperatures.[1][2] This species has been reported to be an agent of fatal brain abscesses in immunologically impaired people.[1][3][11] It can also cause systemic disseminated phaeohyphomycosis[5] affecting other organs including the lungs.[11] Infections due to this species have typically occurred following invasive procedures such as intravenous drug administration and renal transplantation.[11]

In addition to deep mycotic disease, C. atrobrunneum is known to eye diseases including retinitis[15] and keratitis,[16] manifesting with symptoms of pain, redness and watering of the eye, and swelling of the eyelid and surrounding tissues.[16] Corneal infections have responded to dual therapy with topical natamycin and oral ketoconazole.[16] This species has been reported from infections of the skin surrounding the eye.[17] Co-administration of the antifungal drugs fluconazole (delivered topically) and itraconazole (delivered orally) have been effective in the treatment of cutaneous disease.[17] Skin infections are thought to result from direct contact with environmental reservoirs of C. atrobrunneum such as soil, and accordingly farmers or children may have greater susceptibility.[17]

References
  1. Barron, M.A.; Sutton, D.A.; Veve R.; Guarro J.; Rinaldi, M.; Thompson E.; Cagnoni P.J.; Moultney K.; Madinger N.E. (2003). "Invasive Mycotic Infections Caused by Chaetomium perlucidum, a New Agent of Cerebral Phaeohyphomycosis". Journal of Clinical Microbiology. 41 (11): 5302–5307. doi:10.1128/jcm.41.11.5302-5307.2003. PMC 262481. PMID 14605190.
  2. Liu, Dongyou (2011). Molecular Detection of Human Fungal Pathogens. Boca Raton, Florida: CRC Press. ISBN 9781439812419.
  3. Howard, Dexter H. (2003). Pathogenic Fungi in Humans and Animals. New York, NY: Marcel Dekker Inc. ISBN 9780824706838.
  4. Mukerji, K.G.; Manoharachary, C. (2010). Taxonomy and Ecology of Indian Fungi. New Delhi, India: I.K. International Publishing House. ISBN 9789380026923.
  5. Paterson, R.M.; Lima, N. (2015). Molecular Biology of Food and Water Borne Mycotoxigenic and Mycotic Fungi. Boca Raton, Florida: CRC Press. ISBN 9781466559882.
  6. Ames, L.M. (1949). "New Cellulose Destroying Fungi Isolated from Military Material and Equipment". Mycologia. 41 (6): 637–648. doi:10.2307/3755020. JSTOR 3755020.
  7. Ellis M.B.; Ellis J.P. (1998). Microfungi on Miscellaneous Substrates: An Identification Handbook. Slough, England: The Richmond Publishing Co. Ltd. ISBN 0855462485.
  8. Udagawa, SI; Takada, M (1968). "Notes on some Japanese Ascomycetes VII". Nippon Kingakukai Kaiho (Transactions of the Mycological Society of Japan). 22: 43–49.
  9. Seth, Hari K. (1970). "A monograph of the genus Chaetomium". Nova Hedwigia. Beihefte. Germany: J. Cramer. 37: 133 pp.
  10. Anderson, B.; Frisvad J.C.; Sondergaard I.; Rasmussen I.S.; Larsen L.S. (2011). "Associations between Fungal Species and Water-Damaged Building Materials". Applied and Environmental Microbiology. 77 (12): 4180–4188. doi:10.1128/aem.02513-10. PMC 3131638. PMID 21531835.
  11. Abbott, S.P.; Sigler, L.; McAleer, R.; McGough, D.A.; Rinaldi, M.G.; Mizell, G. (1995). "Fatal Cerebral Mycoses Caused by the Ascomycete Chaetomium strumarium". Journal of Clinical Microbiology. 33 (10): 2692–8. doi:10.1128/JCM.33.10.2692-2698.1995. PMC 228557. PMID 8567907.
  12. Siu, R.G.H. (1951). Microbial decomposition of cellulose. New York: Reinhold.
  13. Atlas, R.M. (2010). Handbook of Microbiological Media (Fourth ed.). Boca Raton, Florida: CRC Press. ISBN 9781439804063.
  14. Hwang E.I.; Yun B.S.; Kim Y.K.; Kwon B.M.; Kim H.G.; Lee H.B.; Bae K.S.; Kim S.U. (2000). "Chaetoatrosin A, a Novel Chitin Synthase II Inhibitor Produced by Chaetomium atrobrunneum F449". The Journal of Antibiotics. 53 (3): 248–55. doi:10.7164/antibiotics.53.248. PMID 10819295.
  15. Tabbara, Khalid F.; Wedin, Keith; Al Haddab, Saad (2010). "Chaetomium Retinitis". Retinal Cases & Brief Reports. 4 (1): 8–10. doi:10.1097/ICB.0b013e31819b19b3. PMID 25390107.
  16. Balne P.K.; Nalamada S.; Kodiganti M.; Taneja M. (2012). "Fungal Keratitis Caused by Chaetomium atrobrunneum". Cornea. 31 (1): 94–95. doi:10.1097/ico.0b013e31821eeaed. PMID 22045390. S2CID 34409097.
  17. Zhang, H.; Ran, Y.; Li, D.; Liu, Y.; Xiang, Y.; Zhang, R.; Dai, Y. (2010). "Clavispora lusitaniae and Chaetomium atrobrunneum as Rare Agents of Cutaneous Infection". Mycopathologia. 169 (5): 373–380. doi:10.1007/s11046-009-9266-9. PMID 20020214. S2CID 24845050.
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