Pseudallescheria boydii is a species of fungus classified in the Ascomycota. It is associated with some forms of eumycetoma/maduromycosis and is the causative agent of pseudallescheriasis. Typically found in stagnant and polluted water, it has been implicated in the infection of immunocompromised and near-drowned pneumonia patients. Treatment of infections with P. boydii is complicated by  resistance to many of the standard antifungal agents normally used to treat infections by filamentous fungi.Pseudallescheria boydii fungal infection was the cause of death in three athletes submerged in the Yarkon River after a bridge collapsed during the 1997 Maccabiah Games. Taxonomy
The fungus was originally described by American mycologist Cornelius Lott Shear in 1922 as a species of Allescheria. Shear obtained cultures from a patient of the Medical Department of the University of Texas. The microbe was apparently associated with a penetrating thorn the patient had incurred in his ankle while running barefoot 12 years before. The diseased area was found to contain hyphae-containing granules that, when cultured, led to the growth of the organism. Shear considered the fungus most closely related to Eurotiopsis gayoni (now called Allescheria gayoni). The specific epithet boydii refers to Dr. Mark F. Boyd, who sent Lott the specimen. David Malloch moved the species to the newly created genus Petriellidium in 1970. The genus name of Petriellidium was in honour of Lionello Petri (1875-1946), who was an Italian botanist (Mycology) and Phytopathologist from Florence.
The species was then transferred to the genus Pseudallescheria in 1982 when examination of the type specimens of Petriellidium and Pseudallescheria revealed that they were the same genus. Ecology
An ability to tolerate minimal aeration and high osmotic pressure enables P. boydii to grow on soil, polluted and stagnant water and manure. Although this fungus is commonly found in temperate climates, it is thermotolerant and can survive in tropical climates and in environments with low oxygen pressure. Growth of P. boydii  can be seen in environments where nitrogen-containing compounds are common, usually due to human pollution. Its ability to use natural gas and other volatile organic compounds suggests a capacity for bioremediation. Growth and morphology
Pseudallescheria boydii is a saprotrophic fungus with broad hyphae growing up to 2–5 μm in width. Colonies change in colour from white to pale brown and develop a cottony texture with maturity. After a 2–3 week incubation period, cleistothecia may form containing asci filled with eight fusiform, one-celled ascospores measuring 12–18 × 9–13 μm in diameter. This fungus grows on most standard media, maturing in 7 days. Its primary nutrients are the sugars xylose, arabinose, glucose, sucrose, ribitol, xylitol and L-arabinitol. It cannot assimilate maltose or lactose; however, it is able to assimilate urea, asparagine, potassium nitrate and ammonium nitrate. The optimal temperature for growth is 25 °C (77 °F) and the fungus is generally considered to be mesophilic, although it can grow at higher temperatures (up to 37 °C (99 °F)) as well.