Parasitic polymorphism of Coccidioidesspp

Abstract

BackgroundCoccidioides spp. is the ethiological agent of coccidioidomycosis, an infection that can be fatal. Its diagnosis is complicated, due to that it shares clinical and histopathological characteristics with other pulmonary mycoses. Coccidioides spp. is a dimorphic fungus and, in its saprobic phase, grows as a mycelium, forming a large amount of arthroconidia. In susceptible persons, arthroconidia induce dimorphic changes into spherules/endospores, a typical parasitic form of Coccidioides spp. In addition, the diversity of mycelial parasitic forms has been observed in clinical specimens; they are scarcely known and produce errors in diagnosis.MethodsWe presented a retrospective study of images from specimens of smears with 15% potassium hydroxide, cytology, and tissue biopsies of a histopathologic collection from patients with coccidioidomycosis seen at a tertiary-care hospital in Mexico City.ResultsThe parasitic polymorphism of Coccidioides spp. observed in the clinical specimens was as follows: i) spherules/endospores in different maturation stages; ii) pleomorphic cells (septate hyphae, hyphae composed of ovoid and spherical cells, and arthroconidia), and iii) fungal ball formation (mycelia with septate hyphae and arthroconidia).ConclusionsThe parasitic polymorphism of Coccidioides spp. includes the following: spherules/endospores, arthroconidia, and different forms of mycelia. This knowledge is important for the accurate diagnosis of coccidioidomycosis. In earlier studies, we proposed the integration of this diversity of forms in the Coccidioides spp. parasitic cycle. The microhabitat surrounding the fungus into the host would favor the parasitic polymorphism of this fungus, and this environment may assist in the evolution toward parasitism of Coccidioides spp.

Comparative Phylogenomics of Pathogenic and Nonpathogenic Species

“…Mature spherules continue to expand until they rupture, releasing endospores, which then enlarge to continue the spherule growth cycle; endospores can enter the bloodstream and disseminate to almost any soft tissue, where they may cause serious disease ( Cox and Magee 2004 ). Additional parasitic growth forms have been described from coccidioidomycosis patients: pleomorphic hyphae cells and fungal balls (formed by septate hyphae) ( Hagman et al 2000 ; Munoz-Hernandez et al 2014 ).…”

Morphology Changes in Human Fungal Pathogens upon Interaction with the Host

“…Coccidioides spp. are thermally dimorphic and evolutionarily closely related to other thermal dimorphs [ 69 ]. However, Coccidioides can produce large spherules upon inhalation, in which yeast-like endospores develop ( Figure 5 b).…”

“…However, Coccidioides can produce large spherules upon inhalation, in which yeast-like endospores develop ( Figure 5 b). Mature spherules are too large (30–80 µm) to be phagocytosed, resulting in the hypothesis that they provide a protected environment for cellular replication [ 69 ]. Upon rupture, endospores that are produced within the spherule are released and can survive within phagocytes [ 69 ].…”

“…Mature spherules are too large (30–80 µm) to be phagocytosed, resulting in the hypothesis that they provide a protected environment for cellular replication [ 69 ]. Upon rupture, endospores that are produced within the spherule are released and can survive within phagocytes [ 69 ]. Dissemination of Coccidioides from the lungs to secondary tissues is thought to be via the endospores.…”

Dust Devil: The Life and Times of the Fungus That Causes Valley Fever

“…Each endospore can initiate a new spherule, or, under particular atmospheric conditions, nutrient changes, and/or lower temperature, the endospore can convert to a mycelium and initiate the saprobic phase. This occurs in rare circumstances in the living host [ 45 ], but is found most commonly in the environment.…”