Morphology
Mycelia of Paracoccidioides spp. present slow growth when cultured on Sabouraud, Mycosel®, or potato dextrose agars. Initially the colony displays a white, cotton-like surface. Over time, the colony becomes white to beige, while the surface takes a wrinkled aspect with the presence of fissures, resembling popcorn.
The microscopy shows thin, septate hyphae, which might present the infective arthroconidia (also referred to as arthroaleurioconidia or planoconidia). These conidia may vary in abundance and in sizes, according to its genotypes or cryptic species (Theodoro et al. 2012).The macroscopic morphology of the yeast colony shows a cerebriform aspect and beige color. The yeast form grows within 5-7 days of culturing at 37 °C on Sabouraud, Mycosel®, and GPY (glucose, peptone, yeast extract) agars. Microscopically a large rounded yeastlike cell appears (6-30 μm in diameter), with thick cell walls, birefringent, with buds varying in number and size. The buds generally range from 2 to 10 μm in diameter and are connected to the parent cell by a narrow isthmus, different from that observed in Blastomyces dermatitidis, in which the single bud is usually broad-based. The presence of large cells, surrounded by numerous small buddings, is classically known as “pilot wheel.” A typical “Mickey mouse cap” can also be observed in culture and in histopathological slides.
6.2.2