 |
|
|
|
|
|
 Introduction
Human
Veterinary
Environmental
Industrial
Agricultural
MSG
Introduction
Medical
Veterinary
Environmental
Industrial
Agricultural
Introduction
Susceptibility
MIC Database
Procedures
Histopathology
Introduction
Abbreviations
Links
CME
Conference
Highlights
Bibliography
Glossary
Good Books
Events Calendar
Introduction
Our Mission
Editorial Board
Editorial Staff
Supporters
Contributors
Legal Stuff
Privacy Policy
Kudos
Introduction
Descriptions
Synonyms
Image Bank
Lecture Bank
Video Bank
This page updated:
1/27/2007 9:23:00 AM
DoctorFungus - All Rights Reserved
© 2007 Copyright
& Privacy Policy
Site built and designed for doctorfungus by Webillustrated
|
 |
 |
|
|
You are here:
The Fungi
> Descriptions >
|
Hortaea werneckii
(described by McGinnis and Schell in 1985)
| |
Kingdom: Fungi
Phylum: Ascomycota
Class: Euascomycetes
Order: Dothideales
Family: Dothioraceae
Genus: Hortaea
Hortaea werneckii is a dematiaceous yeast that inhabits the soil, particularly in tropical and subtropical climates. It is halophilic and has also been isolated from saltwater fish. Hortaea werneckii is an occasional cause of human infections [2202].
Hortaea werneckii is the only species classified in the genus Hortaea. This particular fungus has previously been classified in various other genera and the genus Hortaea appears as its most currently accepted classification. See the list of obsolete names and synonyms for older names of Hortaea werneckii.
Hortaea werneckii is the causative agent of Tinea nigra. Tinea nigra is a superficial infection of stratum corneum. The infection is mostly acquired via direct inoculation of the fungus onto the skin due to contact with soil, wood, and decaying vegetation. The lesions of tinea nigra are usually located on palms but may occasionally involve other parts of the body, such as soles of the feet. These lesions are typically brown to black, flat, not scaly, and with irregular contours. They resemble and must be differentiated from those of malignant melanoma and junctional nevus [150, 970, 2261, 2464].While most of the patients do not have any symptoms related to these lesions, some may have itching.
The colonies of Hortaea werneckii grow slowly and mature within 21 days. From the front, they are initially pale in color, moist, shiny, and yeast-like. In time, these colonies become velvety, olive black, and are covered with a thin layer of mycelium. From the reverse, the color is black. Hortaea werneckii is halophilic. It can tolerate and grow in existence of 10% NaCl. Significantly, it does not grow at 37°C [531, 1295, 2144, 2202].
Septate hyphae, (bicellular) yeast-like conidia, and chlamydospores are observed. The yeast-like conidia (2-5 x 5-10 µm) are the initial structures observed in the early phase of the colony development. These cells have a round end and a tapered and elongated annelidic neck part. They are hyaline initially and become pale olivaceous in time. They function as annellides and produce new annelloconidia. Some of the yeast-like conidia have a central septum and are bicellular. They may gradually be converted to chlamydospore-like cells. Septate, thick-walled, and brown hyphae (up to 6 µm wide) are formed as the colony ages. The annelloconidia are formed at intercalary and lateral annellidic points along the hyphae [531, 1295, 2144, 2202].
Hyperkeratosis (abnormal thickening of the cornified epidermis) is observed. The layers of cornified epidermis are separated by branched hyphae.
Aureobasidium
Exophiala
Wangiella
Some biochemical and growth characteristics, such as decomposition of casein and tyrosine, growth in 15% NaCl, KNO3 assimilation, and maximum growth temperature aid in differentiation of Hortaea werneckii from Exophiala jeanselmei and Wangiella dermatitidis [1295]. Also, the annelated zones of Hortaea werneckii are much broader than those of Exophiala [531].
No special precautions other than general laboratory precautions are required.
Very few data are available. MICs of terbinafine, amphotericin B, itraconazole, and voriconazole tend to be low for isolates of Hortaea werneckii [1490, 1492].
Scraping of the visible affected skin constitutes the primary step in treatment of tinea nigra. It should be performed prior to the application of topical antifungal agents. Topical agents , such as ketoconazole [344] and miconazole [1080, 1437], cicloprox olamine [2038], or terbinafine [2085] are used to treat tinea nigra. Interestingly, topical application of thiabendazole suspension has also been shown to clear the lesions of tinea nigra [380, 2172]. Systemic therapy is not recommended and usually not required [2038]. Oral itraconazole has been succesfully used in some cases [953].
PubMed
GenBank
|
|
References
150. Babel, D. E., J. M. Pelachyk, and J. P. Hurley. 1986. Tinea nigra masquerading as acral lentiginous melanoma. J Dermatol Surg Oncol. 12:502-4.
344. Burke, W. A. 1993. Tinea nigra: treatment with topical ketoconazole. Cutis. 52:209-11.
380. Carr, J. F., and C. W. Lewis. 1975. Tinea nigra palmaris. Treatment with thiabendazole topically. Arch Dermatol. 111:904-5.
531. de Hoog, G. S., J. Guarro, J. Gene, and M. J. Figueras. 2000. Atlas of Clinical Fungi, 2nd ed, vol. 1. Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands.
953. Gupta, G., A. D. Burden, G. S. Shankland, M. E. Fallowfield, and M. D. Richardson. 1997. Tinea nigra secondary to Exophiala werneckii responding to itraconazole. Br J Dermatol. 137:483-4.
970. Hall, J., and V. E. Perry. 1998. Tinea nigra palmaris: differentiation from malignant melanoma or junctional nevi. Cutis. 62:45-6.
1080. Hughes, J. R., M. K. Moore, and A. C. Pembroke. 1993. Tinea nigra palmaris. Clin Exp Dermatol. 18:481-2.
1295. Larone, D. H. 1995. Medically Important Fungi - A Guide to Identification, 3rd ed. ASM Press, Washington, D.C.
1437. Marks, J. G., R. D. King, and B. M. Davis. 1980. Treatment of tinea nigra palmaris with miconazole. Arch Dermatol. 116:321-2.
1490. McGinnis, M. R., and L. Pasarell. 1998. In vitro evaluation of terbinafine and itraconazole against dematiaceous fungi. Med Mycol. 36:243-6.
1492. McGinnis, M. R., and L. Pasarell. 1998. In vitro testing of susceptibilities of filamentous ascomycetes to voriconazole, itraconazole, and amphotericin B, with consideration of phylogenetic implications. Antimicrob. Agents Chemother. 36:2353-2355.
2038. Sayegh-Carreno, R., W. Abramovits-Ackerman, and G. P. Giron. 1989. Therapy of tinea nigra plantaris. Int. J. Dermatol. 28:46-8.
2085. Shannon, P. L., F. A. Ramos-Caro, B. F. Cosgrove, and F. P. Flowers. 1999. Treatment of tinea nigra with terbinafine. Cutis. 64:199-201.
2144. St-Germain, G., and R. Summerbell. 1996. Identifying Filamentous Fungi - A Clinical Laboratory Handbook, 1st ed. Star Publishing Company, Belmont, California.
2172. Stone, O. J., E. B. Ritchie, and C. J. Willis. 1966. Thiabendazole in dimethylsulfoxide for tinea nigra palmaris. Arch Dermatol. 93:241-2.
2202. Sutton, D. A., A. W. Fothergill, and M. G. Rinaldi (ed.). 1998. Guide to Clinically Significant Fungi, 1st ed. Williams & Wilkins, Baltimore.
2261. Tseng, S. S., S. Whittier, S. R. Miller, and G. L. Zalar. 1999. Bilateral tinea nigra plantaris and tinea nigra plantaris mimicking melanoma. Cutis. 64:265-8.
2464. Yaffee, H. S. 1970. Tinea nigra palmaris resembling malignant melanoma. N Engl J Med. 283:1112.
|
|
|
 |
 |
Home |
Image Bank |
Lecture Bank |
Knowledgebase |
Site Map |
Contact Us |
The Fungi |
Mycoses |
Drugs |
Laboratory |
Education & Tools |
About Us
|
|
|
|