South African researchers are working to combat diseases caused by fungal infections, which affect more than 3m people a year in this country, and globally, 1bn people – with more than 150m cases being severe and life-threatening and causing 1.7m deaths annually.
Experts say the statistics are especially shocking given that before 1980, these were not a major health problem, MedicalBrief reports.
Professor Carlien Pohl-Albertyn, National Research Forum (NRF) SARChI Research Chair in Pathogenic Yeasts, said the WHO recently published a list of priority pathogens in which fungi are classified in critical, high- and medium- priority groups.
“Candida species are found in all three levels and Cryptococcus species in critical and medium groups,” she said.
For these reasons, researchers in the Department of Microbiology and Biochemistry at the University of the Free State (UFS) are researching specific yeasts and investigating new treatment options beyond the established antifungals, with Pohl-Albertyn leading the team.
Multidrug-resistant yeast
One of the yeasts being researched is Candida auris – a multidrug-resistant yeast that can cause severe infections, particularly in people who are hospitalised or have weakened immune systems. C. auris was first identified in 2009 in Japan and has since been reported in around 50 countries.
Pohl-Albertyn said C. auris was particularly concerning because it is often resistant to multiple antifungal drugs and can survive on surfaces in healthcare settings, contributing to its spread between patients, and causing hospital outbreaks.
“It has been designated by the US Centres for Disease Control and Prevention (CDC) as a serious global health threat and listed as the second most critical fungal pathogen in the WHO fungal critical priority group,” she said.
“It possesses virulence factors like increased thermo-tolerance, high salinity tolerance, biofilm formation, and extra cellular enzyme secretion.”
Several projects investigate this pathogenic yeast. All of them started with the development of CRISP-Cas9 gene-editing tools, to be able to delete specific genes in the yeast to study their roles.
Environmental yeast
Another yeast being researched, under the supervision of Prof Olihile Sebolai, is Cryptococcus neoformans, found in trees and soil contaminated with bird droppings. It can be airborne and when inhaled, lodges in the lungs (in alveoli) and can cause primary lung infection, said Pohl-Albertyn.
Cryptococcus neoformans causes Aids-defining illnesses in people living with HIV/Aids, and was the first critical fungal pathogen of concern declared by the WHO.
Dissemination to other organs has been reported where it crosses the epithelium barrier by secreting proteases (a class of enzymes that break down proteins in the host) that compromise the tight junctions between the epithelial cells.
The current UFS projects investigate the interaction between the proteases secreted by C. neoformans and co-infecting viruses, such as SARS-CoV-2 and influenza. The SARS-CoV-2 virus is activated by proteases in the host and proteases also help the influenza virus to enter and infect the host cells.
Since the host proteases are similar to those secreted by C. neoformans, these projects are focused on determining if the yeast proteases can also help the viruses to cause infection.
This project is also extended to study Candida albicans proteases as this is also a common co-infecting yeast in Covid-19 patients.
Another project looks at the application of plants as sources for novel drugs against C. neoformans, particularly important as 75%-80% of African and Asian populations still rely on traditional or complementary/alternative medicines for their primary healthcare needs.
Yeast-contaminated water
“Considering the severity of invasive fungal infection, it is important to study the dissemination and proliferation of various pathogenic or potentially pathogenic fungal species in our surrounding environments,” said Pohl-Albertyn
“Candida, Cryptococcus and also the Rhodotorula species are commonly found in water sources, which warrants investigation into the possibility that fungal infections may occur through contact with yeast-contaminated water.”
See more from MedicalBrief archives:
UFS welcomes WHO’s recognition of fungal infections threat
University of Free State: Fungal infections among COVID-19 patients in ICU
Threat of resistance to anti-fungal drugs under-recognised
CDC reports a rise in multidrug-resistant fungus