EXPLORING THE PHENOTYPIC CHARACTERIZATION OF CRYPTOCOCCUS NEOFORMANS CLINICAL ISOLATES

Cryptococcus neoformans is a human fungal pathogen that can infect the lungs and later spread to the central nervous system. This disease is most associated with immunosuppressed individuals. C. neoformans is distinctive compared to other fungi because of its ability to produce a thick capsule comprised of polysaccharides, proteins, and other molecules, which shield this yeast from environmental stresses. The capsule can also interfere with the hosts’ immune response by dampening the response and preventing phagocytic cells from engulfing the yeast due to its increased size. We hypothesize that variation in capsule size among clinical isolates could result in different patient outcomes, as it could aid the cells in establishing disease and avoiding immune detection. For instance, smaller capsules may enable this yeast to survive better within macrophages through adaptation. These infected macrophages can then travel to other parts of the body and spread the infection, while yeast with large capsules pose a challenge for immune cells to engulf. To test this hypothesis, we carried out in vitro analyses to examine which conditions caused optimal capsule production in C. neoformans isolates from temperature, growth duration, media volume, and other growth conditions. In addition, 162 clinical isolates were evaluated for sensitivity to cell stressors, SDS detergent, and caffeine, that affect cell membrane and cell wall integrity. By identifying the conditions that promote optimal capsule growth–a major virulence factor– for this yeast cell, and those that hinder it, more comprehensive research can be conducted on C. neoformans and other fungi.