Subcutaneous Infection: Mycetoma Description: A mycotic infection of humans and animals caused by a number of different fungi and actinomycetes characterized by draining sinuses, granules and tumefaction. The disease results from the traumatic implantation of the aetiologic agent and usually involves the cutaneous and subcutaneous tissue, fascia and bone of the foot or hand. Sinuses discharge serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species, and are the hallmark of mycetoma. More than 20 species of fungi and bacteria can cause mycetoma. The ratio of mycetoma cases caused by bacteria (actinomycetoma) to those caused by true fungi (eumycetoma) is 197:67 World-wide distribution but most common in bare-footed populations living in tropical or subtropical regions. Aetiological agents include Madurella, Acremonium, Pseudallescheria, Exophiala, Leptosphaeria, Curvularia, Fusarium, Aspergillus etc.

Mycoses: diseases cause by fungi Superficial Cutaneous Subcutaneous Systemic Opportunistic

Clinical manifestations: Mycetoma is a chronic, suppurative infection of the subcutaneous tissue and contiguous bone. The clinical features are fairly uniform, regardless of the organism involved. The feet are the most common site for infection and account for at least two-thirds of cases. Other sites include the lower legs, hands, head, neck, chest, shoulder and arms. Most cases start out as a small hard painless nodule which over time begins to soften on the surface and ulcerate to discharge a viscous, purulent fluid containing grains. The infection slowly spreads to adjacent tissue, including bone, often causing considerable deformity. Sinuses continue to discharge serosanguinous fluid containing the granules which vary in size, color and degree of hardness, depending on the etiologic species. These grains are the hallmark of mycetoma. Mycetoma showing numerous draining sinuses. There is destruction of bone, distortion of the foot, and hyperplasia at the openings of the sinus tracts. Excised mycetoma showing a draining sinus (cut open in this preparation) containing black grains.

Laboratory diagnosis: 1. Clinical Material: Tissue biopsy or excised sinus, serosanguinous fluid containing the granules which vary in size, colour and degree of hardness, depending on the aetiologic species. 2. Direct Microscopy: Serosanguinous fluid containing the granules should be examined using either 10% KOH and Parker ink or calcofluor white mounts, and tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver (GMS). H&E stained tissue section showing blacked grained eumycotic mycetoma caused by Madurella mycetomatis. Interpretation: The presence of white to yellow or black pigmented grains, from a patient with supporting clinical symptoms should be considered significant. Biopsy and evidence of tissue invasion is of particular importance. Remember direct microscopy or histopathology does not offer a specific identification of the causative agent. 3. Culture: Clinical specimens should be inoculated onto primary isolation media, like Sabouraud's dextrose agar. 4. Serology: There are currently no commercially available serological procedures for the diagnosis of mycetoma. 5. Identification: Characteristic clinical, microscopic and culture features. Causative agents: Acremonium sp., Aspergillus nidulans, Madurella grisea, Madurella mycetomatis, Scedosporium apiospermum.

Clinical manifestations: Phaeohyphomycosis Description: A mycotic infection of humans and lower animals caused by a number of dematiaceous (brown-pigmented) fungi where the tissue morphology of the causative organism is mycelial. This separates it from other clinical types of disease involving brown-pigmented fungi where the tissue morphology of the organism is a grain (mycotic mycetoma) or sclerotic body (chromoblastomycosis). The etiological agents include various dematiaceous hyphomycetes especially species of Exophiala, Phialophora, Wangiella, Bipolaris, Exserohilum, Cladophialophora , Phaeoannellomyces, Aureobasidium, Cladosporium, Curvularia and Alternaria. Ajello (1986) listed 71 species from 39 genera as causative agents of phaeohyphomycosis. Clinical manifestations: Clinical forms of phaeohyphomycosis range from localized superficial infections of the stratum corneum (tinea nigra) to subcutaneous cysts (phaeomycotic cyst) to invasion of the brain. Ideally, individual disease states involving an invasive fungal infection by a dematiaceous hyphomycete should be designated by a specific description of the pathology and the causative fungal genus or species (where known); for example "pathology A" caused by "fungus X".

1. Subcutaneous phaeohyphomycosis: Subcutaneous infections occur worldwide, usually following the traumatic implantation of fungal elements from contaminated soil, thorns or wood splinters. Exophiala jeanselmei and Wangiella dermatitidisare the most common agents and cystic lesions occur most often in adults. Occasionally, overlying verrucous lesions are formed, especially in the immunosuppressed patient. Subcutaneous phaeohyphomycosis caused by Exophiala jeanselmei. Subcutaneous phaeohyphomycosis caused by Wangiella dermatitidis.

2. Paranasal sinus phaeohyphomycosis: Sinusitis caused by dematiaceous fungi, especially species of Bipolaris, Exserohilum, Curvularia and Alternaria is increasingly being reported, especially in patients with a history of allergic rhinitis or immunosuppression. 3. Cerebral phaeohyphomycosis: Cerebral phaeohyphomycosis is a rare infection, occurring mostly in immunosuppressed patients following the inhalation of conidia. However, cerebral infections caused by Cladophialophora bantianahave been reported in a number of patients without any obvious predisposing factors. This fungus is neurotropic and dissemination to sites other than the CNS is rare.

Laboratory diagnosis: 1. Clinical material: Skin scrapings and/or biopsy; sputum and bronchial washings; cerebrospinal fluid, pleural fluid and blood; tissue biopsies from various visceral organs and indwelling catheter tips. 2. Direct Microscopy: (a) Skin scrapings, sputum, bronchial washings and aspirates should be examined using 10% KOH and Parker ink or calcofluor white mounts; (b) Exudates and body fluids should be centrifuged and the sediment examined using either 10% KOH and Parker ink or calcofluor white mounts, (c) Tissue sections should be stained using H&E, PAS digest, and Grocott's methenamine silver (GMS). Interpretation: The presence of brown pigmented, branching septate hyphae in any specimen, from a patient with supporting clinical symptoms should be considered significant. Biopsy and evidence of tissue invasion is of particular importance. Remember direct microscopy or histopathology does not offer a specific identification of the causative agent. Note: direct microscopy of tissue is necessary to differentiate between chromoblastomycosis which is characterized by the presence in tissue of brown pigmented, planate-dividing, rounded sclerotic bodies and phaeohyphomycosis where the tissue morphology of the causative organism is mycelial. 3. Culture: Clinical specimens should be prepared as outlined in the chapter 2 and inoculated onto primary isolation media, like Sabouraud's dextrose agar. Culture of Cladosporium [left] and Phialophora [right] showing typical brown, olivaceous black or black colony colour for a dematiaceous hyphomycete.

Interpretation: The dematiaceous hyphomycetes involved are well recognized as common environmental airborne contaminants, therefore a positive culture from a non-sterile specimen, such as sputum or skin, needs to be supported by direct microscopic evidence in order to be considered significant. A supporting clinical history in patients with appropriate predisposing conditions, is also helpful. Culture identification is the only reliable means of distinguishing these fungi. 4. Serology: There are currently no commercially available serological procedures for the diagnosis of any of the infections classified under the term phaeohyphomycosis. 5. Identification: Culture characteristics and microscopic morphology are important, especially conidial morphology, the arrangement of conidia on the conidiogenous cell and the morphology of the conidiogenous cell. Cellotape flag and/or slide culture preparations are recommended. Causative agents: Alternaria sp., Aureobasidium pullulans, Bipolaris sp., Cladophialophora bantiana, Curvularia sp., Drechslera sp., Exophiala jeanselmei, Exophiala spinifera, Exophiala sp., Exserohilum sp., Phialophora verrucosa, Wangiella dermatitidis.

Treatment Small, localized lesions are best removed surgically. Eumycetoma infections are mostly resistant to chemotherapy, but oral administration of griseofulvin, 10 mg/kg daily as a single dose for up to 4 weeks, or ketoconazole, 200-400 mg daily for up to 2 weeks, or parnteral administration of amphotericin B, 0.25-1.0 mg/kg daily by infusion for 10-14 days, can be tried. Ketoconazole is effective in about 50% of infections caused by the fungus Madurella mycetomatis. In contrast, actinomycetoma is usually responsive to dapsone or sulfonamides administered over a period of 4-6 months either alone or in combination with rifampicin or streptomycin. Sulfamethoxazole/trimethoprim in combination with streptomycin has also been used. Advanced cases may need radical surgery.