Israeli Scientists Find Yeast Could Prevent Life-Threatening Fungal Infections

(l-r): Dr. Jarmila Sekeresova Kralova, Catalina Donic and Prof. Steffen Jung (Weizmann Institute of Science)

Imagine if yeast can be used to fight life-threatening fungal infections. Well, Israeli researchers at the Weizmann Institute of Science have identified a yeast that might be used to prevent invasive candidiasis, a major cause of death in hospitalized and immunocompromised patients.

Did you see “The Last of Us?” It is a television show about the world being destroyed in a global pandemic caused by a mass fungal infection that turns people into zombie-like creatures. The disease in question in the show is cordyceps, a fungal parasite that as of now can only affect small bugs. OK, that is just a TV show. But there are plenty of other dangerous fungi that can harm human beings.

The study from the Weizmann Institute published in the Journal of Experimental Medicine (JEM), however, deals with a very real disease: it shows that the novel yeast lives harmlessly in the intestines of mice and humans, and – as has so far been shown in laboratory animals – it can displace the yeast responsible for candidiasis, Candida albicans.

Millions of microbial species live within or on the human body, many of them harmless or even beneficial to human health. Among these are various species of yeast, which belong to the fungus kingdom. The microscopic yeast Candida albicans, commonly found in the intestines and the body’s inner cavities, is usually benign, though occasionally it may overgrow and cause superficial infections commonly known as thrush. Under certain circumstances, however, the yeast may penetrate the intestinal barrier and infect the blood or internal organs. This dangerous condition, known as invasive candidiasis, is commonly seen in healthcare environments, particularly in immunocompromised patients, with mortality rates of up to 25 percent.

Like many scientific breakthroughs, this research began with a serendipitous finding. While studying yeast infections, Prof. Steffen Jung and colleagues at the Weizmann Institute noticed that some of their laboratory mice could not be colonized with C. albicans, but rather carried a previously unknown species of yeast.

“Knowing that C. albicans can cause life-threatening disease, we decided to investigate this further,” Jung says. “And indeed, this line of research paid off – we found that the novel yeast could robustly prevent colonization with C. albicans.”

The researchers named the new species Kazachstania weizmannii, in honor of Dr. Chaim Weizmann, Israel’s first president and founder of the Weizmann Institute. This species is closely related to yeast associated with sourdough production and appears to live innocuously in the intestines of mice, even when the animals are immunosuppressed.

But most importantly, the researchers found that K. weizmannii can outcompete C. albicans for its place within the gut, reducing the population of C. albicans in mouse intestines. Moreover, although C. albicans can cross the intestinal barrier and spread to other organs in immunosuppressed mice, exposure of such animals to K. weizmannii significantly delayed the onset of invasive candidiasis.

Notably, Jung and colleagues also identified K. weizmannii and other, similar species in human gut samples. Their preliminary data suggest that the presence of K. weizmannii was mutually exclusive with the presence of Candida species, suggesting that the two species might also compete with each other in human intestines, although these findings need to be substantiated by further analyses.

“By virtue of its ability to successfully compete with C. albicans in the mouse gut, K. weizmannii reduced the presence of C. albicans and mitigated candidiasis development in immunosuppressed animals,” Jung says. “This competition between Kazachstania and Candida species might possibly have therapeutic value for the management of human diseases caused by C. albicans.”