Scytalidium hyalinum
| Scytalidium hyalinum | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Leotiomycetes |
| Order: | Helotiales |
| Genus: | Scytalidium |
| Species: | S. hyalinum
|
| Binomial name | |
| Scytalidium hyalinum C.K. Campb. & J.L. Mulder
| |
Scytalidium hyalinum is an ascomycete fungus currently in the genus Scytalidium. It causes dermatomycosis and systemic infections in humans and it is widespread throughout the world.
Taxonomy
[edit]Scytalidium hyalinum was first isolated in 1977 in England by C.K. Campbell.[1] It was isolated from 8 immigrants from Jamaica, Nigeria, and Sierra Leone who had shown signs of tinea pedis and skin infections.[1]
It is unclear whether S. hyalinum and Neoscytalidium dimidiatum are very closely related or if S. hyalinum is a same species mutation of N. dimidiatum. Comparisons of several N. dimidiatum and S. hyalinum strains have found that all S. hyalinum strains differed from the N. dimidiatum strains by a single A-G polymorphism at position 144 and by the absence of an IE intron group that is present in N. dimidatum, [2][3] which suggests they are different species.
Description
[edit]Colonies on malt agar grow rapidly at 27 °C (81 °F) and produce white fluffy superficial mycelia as well as immersed mycelia.[1] Hyphae are up to 4 μm in width, pale or colorless, septate, and smooth. Stromata are absent. Conidiophores are unusually small (micronematous), can be branched or unbranched, pale or colorless, straight, smooth, and irregular. Conidia are arthrosporic, simple, cylindrical to ellipsoid or rounded, sometimes rough, catenulate, separating, hyaline or pale, with thin cell walls.[1]
Colonies are visible after only a few days of growth on Sabouraud’s dextrose agar.[4] Fungal growth is robust at 37 °C (99 °F), the temperature of the human body.[5] Growth is poor above 40 °C (104 °F), but colonies can survive at 42 °C (108 °F) for two weeks.[5]
Scytalidium hyalinum is able to hydrolyse gelatin, casein, tyrosine, olive oil, and urea.[5]
Ecology
[edit]It is most likely endemic to West Africa,[1][6] the West Indies,[1] and the Pacific.[7] It is also present in the UK,[1] Spain,[6] Italy,[8] Australia,[9] and France[10] via travel and immigration. Until 2007, when it was recovered from soil in Indian rat burrows in India, S. hyalinum had never been isolated from the environment.[7][11]
Pathogenicity
[edit]Infection resembles N. dimidiatum infections. Lesions are confined to hands, feet, and toenails.[4] The fungus is found in the toewebs and nails. Nail changes involve thickening, yellow-brown discoloration, and subungual keratosis. It can cause distinctive thickening, lichenification, and discoloration of the knuckles and sides of fingers, but it is not consistent.[4] More than half of patients reported itching at site of infection.[7] Infections are usually chronic, which suggests that the immune response is ineffective or deficient.[12][7]
Scytalidium hyalinum can present a mixed infection with N. dimidiatum.[1][4] The infections of both S. hyalinum and N. dimidiatum are virtually clinically indistinguishable from the chronic, non-inflammatory dry type of Trichophyton rubrum infection.[7]
Both S. hyalinum and N. dimidiatum are resistant to treatment by griseofulvin and susceptible to cycloheximide.[1] It is sensitive to clotrimazole and miconazole in vitro.[4] Cases have also been treated with oral itraconazole.[8] An in vitro study suggested that voriconazole could be effective for refractory infections.[13] S. hyalinum is more susceptible to voriconazole than N. dimidiatum, perhaps because of its lack of protective melanin.[13]
Scytalidium hyalinum and N. dimidiatum share a very similar antigenic structure distinct from other pathogenic fungi.[7] The two species also demonstrate cross-reactivity with each other’s antigens and anti-sera derived from patients.[7] Cross-reactivity between N. dimidiatum and S. hyalinum exoantigens has been demonstrated in both immunodiffusion tests and fused rocket immunoelectrophoresis tests.[7]
In 2018, the first case of ocular infection by S. hyalinum was documented in France.[10] Infection causes pain, red, dry eyes as well as abscesses on the cornea. Prognosis for ocular infections is poor, however it may be that the fungus was only able to cause infection because of reduced immune response in the patient. Treatment with antibiotics and fortified eye drops can be successful. The only other recorded ocular infection by a Scytalidium is N. dimidiatum.
References
[edit]- ^ a b c d e f g h i Campbell, CK; Mulder, JL (1977). "Skin and nail infection by Scytalidium hyalinum sp. nov". Sabouraudia. 15 (2). Medical Mycology: 161–166. doi:10.1080/00362177785190241. PMID 905921.
- ^ Machouart-Dubach, Marie; Lacroix, Claire; Vaury, Christelle; Feuilhade de Chauvin, Martine; Bellanné, Christine; Derouin, Francis; Lorenzo, Frédéric (2002-03-05). "Nucleotide structure of the Scytalidium hyalinum and Scytalidium dimidiatum 18S subunit ribosomal RNA gene: evidence for the insertion of a group IE intron in the rDNA gene of S. dimidiatum". FEMS Microbiology Letters. 208 (2): 187–196. doi:10.1111/j.1574-6968.2002.tb11080.x. ISSN 0378-1097. PMID 11959435.
- ^ Machouart, M.; Lacroix, C.; Bui, H.; Feuilhade de Chauvin, M.; Derouin, F.; Lorenzo, F. (2004-09-15). "Polymorphisms and intronic structures in the 18S subunit ribosomal RNA gene of the fungi Scytalidium dimidiatum and Scytalidium hyalinum. Evidence of an IC1 intron with an His-Cys endonuclease gene". FEMS Microbiology Letters. 238 (2): 455–467. doi:10.1016/j.femsle.2004.08.011. ISSN 0378-1097. PMID 15358433.
- ^ a b c d e Peiris, S.; Moore, M. K.; Marten, R. H. (May 1979). "Scytalidium hyalinum infection of skin and nails". The British Journal of Dermatology. 100 (5): 579–584. doi:10.1111/j.1365-2133.1979.tb05584.x. ISSN 0007-0963. PMID 444431. S2CID 8687033.
- ^ a b c Gugnani, H.C.; Oyeka, C.A. (January 1989). "Foot infections due to Hendersonula toruloidea and Scytalidium hyalinum in coal miners". Medical Mycology. 27 (3): 169–179. doi:10.1080/02681218980000231. ISSN 1369-3786.
- ^ a b Moore, Mary K.; Del Palacio-Hernanz, A.; Lopez-Gomez, S. (January 1984). "Scytalidium hyalinum infection diagnosed in Spain". Medical Mycology. 22 (3): 243–245. doi:10.1080/00362178485380381. ISSN 1369-3786.
- ^ a b c d e f g h Moore, M.K.; Hay, R.J. (October 1986). "Circulating antibodies and antigenic cross-reactivity in Hendersonula toruloidea and Scytalidium hyalinum infections". British Journal of Dermatology. 115 (4): 435–445. doi:10.1111/j.1365-2133.1986.tb06238.x. ISSN 0007-0963. PMID 3778813. S2CID 45577455.
- ^ a b Romano, C (January 1999). "Two cases of tinea pedis caused by Scytalidium hyalinum". Journal of the European Academy of Dermatology and Venereology. 12 (1): 38–42. doi:10.1016/S0926-9959(98)00106-8. PMID 10188148.
- ^ Maslen, Mary M.; Hogg, Geoffrey G. (December 1992). "Scytalidium hyalinum Isolated from the Toe Nail of an Australian Patient". Australasian Journal of Dermatology. 33 (3): 165–168. doi:10.1111/j.1440-0960.1992.tb00112.x. ISSN 0004-8380. PMID 1303078. S2CID 6334690.
- ^ a b Abdellaoui, T.; Ajhoun, Y.; Omari, A.; Benjelloun, N.; Zerrouk, R.; Elasri, F.; Lmimouni, B.; Reda, K.; Oubaaz, A. (2018-04-01). "Endophtalmie sur kératomycose d'étiologie exceptionnelle : Scytalidium hyalinum". Journal Français d'Ophtalmologie (in French). 41 (4): e151–e154. doi:10.1016/j.jfo.2017.06.024. ISSN 0181-5512. PMID 29655576.
- ^ Gugnani, H. C.; Paliwal-Joshi, A.; Rahman, H.; Padhye, A. A.; Singh, T. S. K.; Das, T. K.; Khanal, B.; Bajaj, R.; Rao, S.; Chukhani, R. (November 2007). "Occurrence of pathogenic fungi in soil of burrows of rats and of other sites in bamboo plantations in India and Nepal". Mycoses. 50 (6): 507–511. doi:10.1111/j.1439-0507.2007.01402.x. ISSN 0933-7407. PMID 17944715. S2CID 23477272.
- ^ Carruthers, J. A.; Stein, L.; Black, W. A. (1982-10-01). "Persistent skin and nail infection by an exotic fungus, Hendersonula toruloidea". Canadian Medical Association Journal. 127 (7): 608. ISSN 0008-4409. PMC 1862163. PMID 7127230.
- ^ a b Lacroix, C.; de Chauvin, M. F. (2008-02-04). "In vitro activity of amphotericin B, itraconazole, voriconazole, posaconazole, caspofungin and terbinafine against Scytalidium dimidiatum and Scytalidium hyalinum clinical isolates". Journal of Antimicrobial Chemotherapy. 61 (4): 835–837. doi:10.1093/jac/dkn011. ISSN 0305-7453. PMID 18218642.