The ability of microorganisms to colonise and display an intracellular lifestyle within a host body increases their fitness to survive and avoid extinction. This host–pathogen association drives microbial evolution, as such organisms are under selective pressure and can become more pathogenic. Some of these microorganisms can quickly spread through the environment via transmission. The non-transmittable fungal pathogens, such as Cryptococcus, probably return into the environment upon decomposition of the infected host. This review analyses whether re-entry of the pathogen into the environment causes restoration of its non-pathogenic state or whether environmental factors and parameters assist them in maintaining pathogenesis. Cryptococcus (C.) neoformans is therefore used as a model organism to evaluate the impact of environmental stress factors that aid the survival and pathogenesis of C. neoformans intracellularly and extracellularly.

Cryptococcus neoformans (C. neoformans) has emerged as a global pathogen of concern. While much is known about its pathobiology, its management is complicated by strains displaying non-fluconazole susceptibility. This contribution assessed the repurposing of artemisinin (ART) as an anti-Cryptococcus antifungal. An in vitro susceptibility assay was performed to assess the drug response of cells. To establish the ART mode of action, assays examining mitochondrial health were set up. The phagocytosis efficiency of a murine macrophage cell line towards ART-treated and non-treated cells was determined. To complement this, the immunomodulatory effects of ART were further characterised in Galleria mellonella (G. mellonella) by assessing haemocytes’ phagocytosis and expression of immune genes, i.e., insect metalloproteinase inhibitor (IMPI) and hemolin, essential for the insect antimicrobial response. In the end, the survival rate of infected larvae was calculated. We established that ART was antifungal, with cell death triggered by the uncoupling of the cytochrome c (cyt c) from the mitochondria, leading to activation of caspase-3-dependent-like apoptosis. Moreover, treatment induced ultrastructural changes with treated cells appearing more deformed than non-treated cells (p < 0.05). Treatment also increased the susceptibility of cells towards both macrophage and haemocyte phagocytosis compared to non-treated cells (p < 0.05). Importantly, treatment seemed to weaken the cells, decreasing their virulence potential based on analysis of the expression of the immune gene markers, which translated into treatment rescuing 75% of the larvae infected with 0.1 ART-treated cells. These preliminary findings support the repurposing of ART as an anti-Cryptococcus antifungal.

Background and Aim: Cryptococcal yeast cells are spread across different ecosystems through bird movement and are deposited in bird guano. These cells may be inhaled by humans and lead to cryptococcal pneumonia. In individuals with reduced immune T-cell populations, cells may disseminate to the brain and cause the often-deadly cryptococcal meningitis. In this study, we surveyed cryptococcal cells in bird droppings across the city of Bloemfontein, South Africa. Materials and Methods: We aseptically collected 120 bird dropping samples from 15 representative city sites. In the laboratory, samples were assessed with regards to location, weighed, and standardized to a mass of 1 g before suspension in 10 mL phosphate buffer saline. Samples were first screened using Calcofluor-white stain as it is a rapid technique for the detection of fungi via binding to cell wall components such as chitin. After this, positive Calcofluor samples were serologically assayed for the cryptococcal antigen (CrAg). To confirm assay data, CrAg positive samples were then cultured on bird seed agar and resulting colonies were assessed using Indian ink. Results: We determined that 10/15 locations were positive for the CrAg. Pathogenic cells were identified on bird seed agar as brown colonies. When examined using microscopy, brown colony cells exhibited characteristic thick capsules representative of cryptococcal cells. Conclusion: This is the first proximate analysis showing the ecological distribution of cryptococcal cells in Bloemfontein. This is important as associated infections are acquired from the environment. Similarly, given the threat posed by cryptococcal cells to immunocompromised individuals, local authorities must initiate measures curbing the spread of these cells.