Fusarium species are ubiquitous soil saprophytes and occasional plant pathogens. They are responsible for a variety of superficial and invasive human infectious diseases. Fusarium moniliforme, Fusarium oxysporum, and Fusarium solani are the most commonly isolated species. These pathogens produce characteristic fusoid or sickle-shaped macroconidia when cultured on synthetic media, but the tissue forms of these fungi are purely hyphal. Fusoid conidia can also be seen in smears from blood cultures growing these organisms.
The hyphae of the Fusarium spp. are 3 to 8 µm in width, are septate, branched, and haphazardly dispersed throughout the lesions. The hyphal branches characteristically arise at right angles from parent hyphae. The hyphae cannot be reliably distinguished from those of Aspergillus spp. Definitive diagnosis requires isolation in culture.
Opportunistic infections frequently begin as cutaneous infections, which manifest clinically as painful, erythematous, or necrotic nodules that enlarge and ulcerate. The fungi can disseminate to the lungs, kidneys, and other organs.
28. CDC/Hardin. Image #17970. Under a magnification of 475X, this photomicrograph of a lactophenol cotton blue-stained specimen, revealed some of the ultrastructural morphology exhibited by a Fusarium sp. fungal organism. Of importance here, were the septate, filamentous hyphae, and the floral arrangement of the fusiform-shaped macroconidia. PHIL public domain. Created 1970. Accessed January 14, 2023. https://phil.cdc.gov/Details.aspx?pid=17970 29. CDC/Hardin. Image #23085. Under a magnification of 475X, this photomicrograph depicted clumps of elongated, sickle-shaped, multicellular macroconidia, exhibited by a Fusarium sp. fungal organism. PHIL public domain. Created 1965. Accessed January 14, 2023. https://phil.cdc.gov/Details.aspx?pid=23085
