Cellular response of host usually absent - no pathology elicited by fungus

1. Organism remote from living tissue (primarily in the stratum corneum - compact dead layer of skin).
2. Infection is insignificant and ignored by bodies defenses.

1. Visual Inspection
2. Wood's lamp - U.V. lamp to look for presence of fluorescence.
3. Scraping off cells onto a slide and clearing tissue with 10% KOH and flaming the slide.  Look for fungal tissue (e.g., mycelial fragments, yeast cells, spores).  These slides are not permanent because the KOH causes cells to breakdown over time - too caustic!
4. Stripping tape - Scotch tape is pulled of skin, mounted on a slide,  and stained with crystal violet, methylene blue, or iodine.
5. Isolation and subculturing of fungus.

• chronic infection of the ear - usually in children.
• Most culprits for this malady are species of  Aspergillus (A. niger), Scopulariopsis, (S. brevicaulis), Penicillium, Mucor, and Rhizopus.
• Some infections are caused by yeast.
• Occasionally, infection may lead to deeper infection involving cutaneous tissue; in these cases inflamation, pruritus (severe itching), scaling, and severe discomfort.
• http://eac.hawkelibrary.com/albums/otomycosis/73_G.jpg
• http://www.doctorfungus.org/mycoses/human/other/otomycosis.htm

Fungal Growth in the Ear Canal

Fungal Growth in Culture (Aspergillus niger)

             l

Scopulariopsis, (S. brevicaulis)

Penicillium

Mucor 

Rhizopus

• hair shaft infect characterized by the presence of firm, irregular nodules
• may cause hair breakage
• infected areas do not fluoresce when exposed to ultraviolet light
• http://www.doctorfungus.org/mycoses/human/other/piedra.htm
• http://www.doctorfungus.org/thefungi/piedraia.htm

• white piedra occurs on hair in the beard, axillary regions, groin region, and less frequently on the scalp.

• found in temperate regions including the U.S., Europe, Orient, and tropics (South America).

• usually associated with poor body hygiene and also in immunosuppressed patients.

• pathogen originates from environment, such as soil, stagnant water, spoiling fruit and food and can be part of the normal skin microflora.

• If sexual or perfect stage of the fungus is ever discovered, most likely it will be a basidiomycete due similarity between the ultrastructure of the hyphal cross walls (dolipore septum is present) of this fungus with those found in the basidiomycetes.

    Black piedra (Piedraia hortae or P. hortai - Refer to Figures 34-36 on page 53 in the textbook)

• caused by an ascomycete that produces stony nodules [stromata] that contain locules with asci and ascospores)
• source of infection is soil

• make slide using infected hair soaked in 10% KOH solution and examine under microscope
• for Piedraia hortae look for locules in the stony stroma and asci (with 8 ascospores).
• for Trichosporon beigelii - material detaches easily form hair shaft; material consists of yeast-like conidia called blastoconidia and a loose network of hyphae. No ascospores are ever seen.

• shaving or cutting away infected hair
• application of topical fungicides ( such as, HgCl₂ (1:2000), benzoic and salicylic acid combinations, 3 percent sulfur ointment or 2 % formalin)

• caused by Malassezia furfur (etiologic or causal agent) and other Malassezia species
• Yeast cells occurs in the stratum corneum - compact dead layer of skin
• cause discovered 150 years ago
• lipophilic yeast (In culture, olive oil is added to medium)
• chronic, mild, usually asymptomatic infection of the stratum corneum
• desquamating (peeling) macules (discolored unraised area of skin)
• skin cells come off in patches with Scotch tape
• fairly common and benign disease
• chest, abdomen, upper limbs, and back
• on lighter skin, the macules appear dark in color
• on darker skin, the macules appear light in color
• exposure with Wood's lamp causes patches to fluoresce yellow to golden
• look at skin scrapings under the microscope (soak skin scrapings with KOH solution to clear tissue) - mycelial fragments and budding yeast cells.
• http://www.doctorfungus.org/mycoses/human/other/Pityriasis_versicolor.htm
• http://dermnetnz.org/fungal/pityriasis-versicolor.html

  Treatment

• topical application of Whitfield's ointment (contains salicylic acid), fungicidal agents such as miconazole, and others to a lesser extent.

• hot soak baths twice a day to remove dead skin.

• washing clothes with Clorox- sodium hypochlorite to disinfest these.

• superficial asymptomatic fungus.
• infection of the stratum corneum characterized by brown to black non-scalelike macules often on the palms of hands.
• etiologic agent - Exophiala werneckii (Sometimes called Cladosporium werneckii).
• the word "tinea", refers to ringworm (in this case, not caused by a dermatophyte), while the word "nigra" refers to black macules associated with this disease.
• resembles a silver nitrate stain but irregular.
• sometimes confused with a malignant melanoma (difference being that melanomas are often raised)
• primarily a tropical disease (Central and South America, Africa and Asia).
• examine skin scrapings to find hyphae, which differ from a dermatophyte (colorless or hyaline hyphae) in being darkly pigmented, often brown to olivaceous in color.
• hyphae are highly branched and septate.

• Whitfield's ointment, miconazole nitrate in a cream base, as well as other imidazoles and triazoles applied topically.
• griseofulvin treatment is not effective
• sulfur ointments
• tincture of iodine

• Mayo Clinic:  Data base for Diseases, Conditions, and Drug Information
• Doctor Fungus