Mycetoma is a chronic subcutaneous infection induced by traumatic inoculation with any of several saprophytic species of fungi or actinomycetous bacteria that are normally found in soil. The clinical features defining mycetoma are local swelling of the infected tissue and interconnecting, often draining, sinuses or fistulae that contain granules, which are microcolonies of the agent embedded in tissue material. An actinomycetoma is a mycetoma caused by an actinomycete; a eumycetoma (maduromycosis, Madura foot) is a mycetoma caused by a fungus. The natural history and clinical features of both types of mycetoma are similar, but actinomycetomas may be more invasive, spreading from the subcutaneous tissue to the underlying muscle. Of course, the therapy is different. Mycetoma occurs worldwide but more often among impoverished people who reside in tropical areas and wear less protective clothing. Mycetomas occur only sporadically outside the tropics but are particularly prevalent in India, Africa, and Latin America. Actinomycetomas are discussed in Chapter 12.
Morphology and Identification
The fungal agents of mycetoma include, among others, P. boydii (anamorph, Scedosporium apiospermum), M. mycetomatis, Madurella grisea, E. jeanselmei, and Acremonium falciforme. In the United States, the prevalent species is P. boydii, which is self-fertile (homothallic) and has the ability to produce ascospores in culture. E. jeanselmei and the Madurella species are dematiaceous molds. These molds are identified primarily by their mode of conidiation. P. boydii may also cause pseudallescheriasis, which is a systemic infection of compromised patients.
In tissue, the mycetoma granules may range up to 2 mm in size. The color of the granule may provide information about the agent. For example, the granules of mycetoma caused by P. boydii and A. falciforme are white; those of M. grisea and E. jeanselmei are black; and M. mycetomatis produces a dark red to black granule. These granules are hard and contain inter twined, septate hyphae (3–5 µm in width). The hyphae are typically distorted and enlarged at the periphery of the granule.
Pathogenesis and Clinical Findings
Mycetoma develops after traumatic inoculation with soil contaminated with one of the agents. Subcutaneous tissues of the feet, lower extremities, hands, and exposed areas are most often involved. Regardless of the agent, the pathology is characterized by suppuration and abscesses, granulomata, and draining sinuses containing the granules. This process may spread to contiguous muscle and bone. Untreated lesions persist for years and extend deeper and peripherally, causing deformation and loss of function.
Very rarely, P. boydii may disseminate in an immunocompromised host or produces infection of a foreign body (eg, a cardiac pacemaker).
Diagnostic Laboratory Tests
Granules can be dissected out from the pus or biopsy mate rial for examination and culture on appropriate media. The granule color, texture, and size and the presence of hyaline or pigmented hyphae (or bacteria) are helpful in determining the causative agent. Draining mycetomas are often superinfected with staphylococci and streptococci.
Treatment
The management of eumycetoma is difficult, involving surgical debridement or excision and chemotherapy. P. boydii is treated with topical nystatin or miconazole. Itraconazole, ketoconazole, and even amphotericin B can be recommended for Madurella infections and flucytosine for E. jeanselmei. Chemotherapeutic agents must be given for long periods to adequately penetrate these lesions.
Epidemiology and Control
The organisms producing mycetoma occur in soil and on vegetation. Barefoot farm laborers are therefore commonly exposed. Properly cleaning wounds and wearing shoes are reasonable control measures.
