Sporothrix

Most mycologists consider it fruitless to directly examine clinical specimens for the yeast form of Sporothrix schenckii. The number of yeast cells in the specimen is typically very limited, and their small size and shape are not distinctive. The yeast form of S. schenckii is not easily seen in sections of tissue stained with hematoxylin and eosin. 

S. schenckii, a dimorphic fungus, is considered the only pathogenic member of the genus Sporothrix. Recently, a new species, Sporothrix cyanescens, was added to the genus. Some of the isolates upon which the species description was based were isolated from patients with mycosis of human skin. Whether or not S. cyanescens is another etiologic agent of sporotrichosis remains to be proven. 

Figure 3.26 Sporothrix schenckii. Taken by phase-contrast microscopy after 2 weeks on potato dextrose agar. Bar equals 10 pm.

Fig. 14.— 13C-N.m.r. Spectrum of /3-D-Glucan(s) from Sporothrix schenckii. (Solvent, DjO temperature, 70° chemical shifts expressed as 8C, relative to external tetramethyl-silane.)...

In dimorphic fungi, the composition of constituent polysaccharides is sensitive to morphology and to the cultural conditions. These effects are accentuated in the case of Sporothrix schenckii, and 13C-n.m.r. spectroscopy can be used to detect individual polysaccharides in a qualitative way. The 13C-n.m.r. spectra of mannose-containing polysaccharides of ten Sporothrix schenckii and three Ceratocystis stenoceras species, grown under various conditions, were distinguishable in terms of the presence of signals,130 at 8C 103.3 to 103.7, which arose from 0-a-L-rhamnopyranosyl-(l- 2)-0-a-L-rhamnopyranosyl-(1— 3)-side-chains (14 C-l, 103.7 C-l, 96.8), and were not present in... 

Fig. 19.—13C-N.m.r. Spectra (Excluding C-CH3 Regions) of Polysaccharides (in D20) Isolated from Various Strains of Sporothrix schenckii. (Polysaccharides A, B, C, and D were isolated from Strains 1099.23, 1099.27, 1099.16, and 1099.18, respectively solvent, D2Oj temperature, 70° chemical shifts expressed as Sc, relative to external tetra-methylsilane.)...

Superflcial mycoses are usually clinically evident (some will fluoresce when using a Wood s lamp) and can be confirmed by microscopy (using KOH solution) and culture of hairs, nails or scrapings from the edge of skin lesions. Species of Microsporum, Trichophyton, Epidermophyton (all moulds), and of Malassezia, Candida, Pityrospo-rum (all yeasts) cause most superflcial infections. Subcutaneous mycoses are caused by Sporothrix... 

Amphotericin B is used to treat systemic disseminated fungal infections caused by Candida spp., Cryptococcus neoformans, and the invasive dimorphic fungi Aspergillus spp., Histoplasma capsulatum, Coccidioides immi-tis, Blastomyces dermatitidis, and Sporothrix schenckii). Intravenous amphotericin B remains the treatment of choice for serious invasive fungal infections unresponsive to other agents. 

Hayashi M, Kim Y-P, Takamatsu S, Preeprame S, Komiya T, Masuma R, Tanaka H, Komiyama K, Omura S (1996) Chlovalicin, a New Cytocidal Antibiotic Produced by Sporothrix sp. FO-4649 I. Taxonomy, Fermentation, Isolation and Biological Activities. J Antibiot 49 631... 

All reports on starchlike polymers cannot be covered herein. However, the cell walls of Fusicoccum amygdali are stained blue with iodine and attacked by alpha amylase.8 Extracts of Sporothrix schenckii... 

A linear cell-wall glucan(s) from Sporothrix schenckii contains 3-0-, 6-0-, and 4-O-substituted /8-D-glucopyranosyI units, the /S-D-glycosi-dic configuration being determined by, 3C-n.m.r. spectroscopy,9 by virtue of the C-l signals, at relatively low field, of 8c 103.8 and 104.8. 

Yeast forms of the dimorphic yeast Sporothrix schenckii, grown at 37°, produce128 rhamnomannan 25, but, at 25°, small proportions of 4-O- and 2,4,di-0-substituted a-D-mannopyranosyl structures129 are formed, as130 in 26, 27, and 28. Structure 25 was formed by alkaline degradation of a peptidorhamnomannan present in the cells and the culture medium.131... 

Toledo, M.S., Levery, S.B., Glushka, J., Straus, A.H., and Takahashi, H.K., 2001, Structure elucidation of sphingolipids from the mycopathogen Sporothrix schenckii Identification of novel glycosylinositol phosphorylceramides with core Manal— 6Ins linkage. Biochem. Biophys. Res. Commun. 280 19-24. 

A problem concerning DNA as the type specimen has been considered by Reynolds and Taylor [146] and Haines and Cooper [147]. Prillinger et al. [148] found that phenotypically identified strains of Sporothrix schenckii may be heterogeneous and stressed the importance of culture collections in modem genotypic identification. 

Within the Stephanoascales Stephanoascus ciferrii and its anamorph C. ciferrii are the only pathogenic species so far. The species is often associated with animals and occasionally isolated from clinical specimens [226] as an agent of human onychomycosis [227]. Some strains are strongly hyphal and produce conidia from characteristically inflated, denticulate heads. This anamorph has been described as Sporothrix catenata. 

Weijman ACM, de Hoog GS Carbohydrate patterns and taxonomy of Sporothrix and Blastobotrys. Antonie Van Leeuwenhoek 1985 51 111-120. 

Sigler L, Harris JL, Dixon DM, Flis AL, Salkin IF, Kemna M, Duncan RA Microbiology and potential virulence of Sporothrix cyanescens, a fungus rarely isolated from blood and skin. J Clin Microbiol 1990 28 1009-1015. 

For systemic treatment of fungal infections in dogs and cats, ketoconazole and fluconazole are available as tablets and oral suspensions, itraconazole as capsules, while miconazole and fluconazole are available as parenteral solutions. Even though ketoconazole is often effective, itraconazole may be the preferred azole for the treatment of systemic disease caused by dimorphic fungi (Blastomyces dermatitidis, Histoplasma capsulatum, Sporothrix schenckii). The activity of fluconazole against dimorphic fungi is limited to coccidioidal disease (Coccidioides immitis), but this azole penetrates the blood-brain barrier. 

Amp B has a wide fungicidal spectrum and remains the DOC (or co-DOC) for severe infections caused by Aspergillus, Candida, Cryptococcus, Histoplasma, Mucor, and Sporothrix. Amp B is synergistic with flucytosine in candidiasis and cryptococcoses. 

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