Researchers at the Weizmann Institute of Science in Israel have identified a yeast that could be used to prevent invasive candidiasis, a major cause of death in hospitalized and immunocompromised patients. The study, to be published March 18 in the Journal of Experimental Medicine (JEM), shows that the novel yeast lives harmlessly in the intestines of mice and humans and can displace the yeast responsible for candidiasis, Candida albicans.

20156_lores

Source: CDC/ Dr. Kaplan

Under a magnification of 500X, this photomicrograph of a Gömöri-trichrome-stained liver tissue specimen revealed the presence of what is known as an asteroid body, containing a number of pseudohyphae of the fungal organism, Candida albicans, in the case of a male patient with systemic candidiasis.

Millions of microbial species live within or on the human body, many of them being harmless or even beneficial to human health. The microscopic yeast C. albicans is commonly found in the intestines and other mucosal surfaces of the body and 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 systemically 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%.

Novel yeast

While studying yeast infections in laboratory mice, Steffen Jung and colleagues at the Weizmann Institute discovered that some of their mice carried a novel species of yeast that prevented the animals from being infected with C. albicans. The new species, which the researchers named Kazachstania weizmannii, 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.

K. weizmannii

Source: © 2024 Sekeresova Kralova et al. Originally published in Journal of Experimental Medicine

C. albicans spreads to the kidneys of immunosuppressed mice (left), but invasive candidiasis is mitigated by exposure to K. weizmannii (right).

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, while C. albicans can cross the intestinal barrier and spread to other organs in immunosuppressed mice, the presence of K. weizmannii in the animals’ drinking water significantly delayed the onset of invasive candidiasis.

Competing in gut

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.

“By virtue of its ability to successfully compete with C. albicans in the murine gut, K. weizmannii lowered the C. albicans burden and mitigated candidiasis development in immunosuppressed animals,” Jung says. “This competition between Kazachstania and Candida species could have potential therapeutic value for the management of C. albicans–mediated diseases.”

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