Suspected Fungi

Suspected fungi that cause problems during jungle training:

Dermatophytes
Dermatophytes, or also known as keratinophilic fungi, produce extracellular enzymes (keratinases) which are capable of hydrolyzing keratin.

There are 3 genera of dermatophytes:

1. Trichophyton species (19 species)
- These infect skin, hair and nails. Rarely can cause subcutaneous infections, in immunocompromised individuals.
- Can be identified by their colony appearence and microscopic morphology.
- Grow for 2 weeks at 25 degree C on Sabouraud's dextrose agar.
- Colonies of T. mentagrophyts may be cottony to granular, display abundant grape-like clusters of spherical micoconidia(small reproductive structures)

http://www2.provlab.ab.ca/bugs/webbug/mycology/tment.htm

- T. rubrum has a white cottony surgace and a deep red, nondiffusible pigment viewed from the reverse side of the colony. Microconidia are small and piriform (pear-shaped).

http://www2.provlab.ab.ca/bugs/webbug/mycology/trub.htm

- T tonsurans produces a flat, powdery velvety colony, becomes reddish-brown on reverse, the microconidia are mostly elongate. http://www2.provlab.ab.ca/bugs/webbug/mycology/ttons.htm

2. Microsporum species (13 species).
- These may infect skin and hair, rarely nails.
- Produce distinctive multicellular macroconidia with echinulate walls.

- This organism could be easily identified on the scalp because infected hairs fluoresce a bright green color when illuminated with a UV-emitting Wood's light.
-M canis forms a colony with a white cottony surface and deep yellow on the reverse. 8 to 15-celled macroconidia frequently have hooked tips.

http://www2.provlab.ab.ca/bugs/webbug/mycology/mcanis.htm

-M gypseum produces a tan, powdery colony and abundant thin-walled. 4 to 6- celled macroconidia. [1]

http://www2.provlab.ab.ca/bugs/webbug/mycology/mgyp.htm

3. Epidermophyton floccosum

- These infect skin and nails and rarely hair.

- They form yellow-colored, cottony cultures and are usually readily identified by the thick, bifurcated hyphae with multiple smooth, club-shaped macroconidia.

Dermatophytes are classfied as geophilic, zoophilic or anthropophilic depending on their usual habitat (soil, animals or humans).

1. It is usually found in the soil and trasmitted to man by direct exposure.
2. It is transmitted to man through close contact with animals (cats, dogs, cows) or with contaminated products.
3. It can be transmited anthrophphilic, which is transmission from man to man by close contact ot through contaminated objects. [1]

Clinical Manifestation:

Tinea means "ringworm", a term to refer to a variety of lesions of the skin or scalp.

Tinea corporis - small lesions occurring anywhere on the body

Tinea pedis - "athlete's foot". Infection of toe webs and soles of feet.
Tinea unguium (onychomycosis) - nails. Clipped and used for culture
Tinea capitis - head. Frequently found in children.
Tinea barbae - ringworm of the bearded areas of the face and neck
Diagnosis is usually possible by direct microscopic examination of KOH-treated skin scrapings which show a typical aspect of mycelia and spores. [1]

Treatment:

Griseoufulvin for 4-6m weeks

-Tolfnatate (Tinactin) available over the counter - Topical

-Miconazole - Topical.
-Ketoconazole
-Itraconazole - oral
-Terbinifine (Lamisil) - oral, topical. [1]

Sporothrix Schenckii

Sporothrix Schenckii is associated with a variety of plants - grasses, trees, sphagnum moss, rose bushes and horticultural plants. Patients usually have a history of trauma associated with outdoor activities and plants.

Clinical findings:

Lesion can be found usually on the extremities and the lesion will develop as a granulomatous nodule that may progress to form a necrotic or ulcerative lesion. [1]

Diagnostic laboratory tests:

- Culture the specimen on Sabouraud's agar containing antibacterial antibiotics and incubate at 25-30 degree C. Identification is confirmed by growth at 35 degree C and conversion to the yeast form.

- Can be examined microscopically with KOH, enhanced sensitivity with routine fungal cell wall stains, such as Gomori's methenamine silver, which stains the cell walls black, or the periodic acid-Schiff stain, which imparts a red colour to the cell walls.

- Can be identified by fluorescent antibody staining. [1]

Chromoblastomycosis

Chromoblastomycosis is a long-term fungal infection of the skin. The infection occurs most commonly in tropical or subtropical climates, often in rural areas. It can be caused by many different type of fungi which become implanted under the skin, often by thorns or splinters. The common types can be Phialophora verrucosa, Cladophialophora carrionii, Rhinocladiella aquaspersa, Fonsecaea pedrosoi and Fonsecaea compacta. [1]

Clnical findings:

The fungi are introduced into the skin by trauma. Over the months to years, the primary lesion becomes verrucous. Cauliflower nodules with crusting abscesses eventually cover the area. Small ulcerations or "black dots" of hemopurulent material are present. [2]

Diagnostic lab tests:

- Scrapings are placed in 10% KOH and examined microscopically for dark, spherical cells. Detection of sclerotic bodies is diagnostic of chromoblastomycosis regardless of the etiologic agent.

- Culture in Sabouraud's agar. Identified by its conidial strucuture, there are many similar saprophytic dematiaceous molds. Unable to grow at 37degree C and being able to digest gelatin. [1]

Treatment:

- Surgical excision with wide margins is the therapy of choice for small lesions.

- Chemotheraphy with flucytosine or iraconazole may be effective for larger lesions.

Blastomyces dermatitidis

Blastomyces dermatitidis is a thermally dimorphic fungus. It specifically inhabits decaying wood material. Isolation from the environment is most likely when the sample contains soil and is rich in organic material such as animal feces, plant fragments, insect remains, and dust. If the substrate is moist, lacks exposure to direct sunlight, contains organic debris, and has a pH of less than 6.0, isolation of isolation of Blastomyces dermatitidis is probable. [2]

Clinical findings:

- The most common clinical presentation is a pulmonary infiltrate in association with a variety symptoms (fever, malaise, night sweats, cough and myalgias) .

- Patient can also present with chronic pneumonia.

- Lesion may evolved into ucerated verrucous granulomas with an advancing border and central scarring. [1]

Diagnostic tests:

-wet mounts of specimen may show broadly attached buds on thick-walled yeast cells

- Colonies usually develop within 2 weeks on Sabouraud's agar at 30 degree C. The identificiation is confirmed by conversion to the yeast form after cultibation on a rich medium at 37 degree C, by extraction and detection of the B dermatidis-specific antigen A, or by a specific DNA probe.

- Antibodies can be measured by CF and ID tests. [1]

Treatment:

- Treat with amphotericin B.

- 6-month course of intraconazole is very effective.


References:

1. Brooks, G. F., Butel, J. S. & Ornston, L. N.; “Jawetz, Melnick & Adeberg’s Medical Microbiology”, 23rd edition, Appleton & Lange, 2004.

2. Wikipedia. (2007). On-site: http://en.wikipedia.org > search >. Retrieved on 19 January 2007.