Probiotic yeasts derived from food help reduce the virulence of deadly fungi

Researchers from the Central Food Technological Research Institute (CFTRI) in Mysore and a counterpart from the US have shown that probiotic yeasts derived from food help reduce, if not wholly nullify, the virulence of certain deadly fungi, which have of late become resistant to commonly-used anti-fungal agents.

A paper published recently in the journal mBio , the CFTRI researchers led by K A Anu-Appaiah and their collaborator Reeta Rao from the Worcester Polytechnic Institute in the US examined the ability of two food-derived yeasts, Saccharomyces cerevisiae and Issatchenkia occidentalis , which grow naturally on fruits and other foods, to combat adhesion and biofilm formation in certain fungi belonging to the Candida family. CFTRI is a premier research laboratory under the aegis of the Council of Scientific and Industrial Research.

The probiotic yeasts are particularly effective against Candida auris, which has been creating a scare after drug-resistant variants were discovered at tertiary healthcare facilities in the US and the UK, among other countries. The bug was said to be present in Indian hospitals since 2011, according to the experts who isolated the drug-resistant pathogen.

While Candida albicans is the leading cause of hospital-acquired fungal infections, the study focused on a number of non- albicans species like C. auris as they can cause similar infections and as many of these strains are developing resistance to available anti-fungal medications.

The scientists found that applying these yeasts to non-biological surfaces reduced the ability of C. auris and others to adhere to these surfaces by as much as 53 per cent. The yeasts also reduced the formation of biofilms by as much as 70 per cent. Applying the food-derived yeasts to surfaces also inhibited a process known as filamentation in several fungi. Filamentation is a mechanism used by virulent fungi to evade the body's immune response and is believed to be essential to adhesion and biofilm formation.

In immune-compromised patients or even healthy individuals with implanted medical devices, Candida can penetrates the submucosal tissue of the gastrointestinal tract and reach the internal organs, where it can cause life-threatening systemic infections. The microbes' drug resistance stems, in part, from their ability to adhere to surfaces and form biofilms. "A biofilm is a complex ecosystem that can become a physical barrier against drugs," Rao, who is the principal author of the paper, said in a statement. "Biofilms can form on medical devices, catheters and IV lines, and even contact lenses. They can also penetrate epithelial tissue in the body, leading to a variety of infections, including the deadly bloodstream infections we can see with C. auris ."

Such fungal infections are a significant concern in Indian hospitals too. Studies have shown that a large number of patients in intensive care units in hospitals here also are getting infected by the fungus.

Anuradha Chowdhary, professor of medical mycology at the Vallabhbhai Patel Chest Institute, in New Delhi, one of the first medical scientists in the country to study C. auris , recently told BusinessLine that almost 90 per cent of the fungal isolates were found to be resistant to fluconazole, the standard anti-fungal drug of choice in many countries. The bug is also developing resistance to other anti-fungal drugs, but slowly. “The problem is that the number of anti-fungal drugs currently available in the market are very few. That is the worry,” said Chowdhary.

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