Neeraj Chauhan, Ph.D., an associate professor in the Center for Discovery and Innovation at Hackensack Meridian Health, explained the mechanisms behind antifungal resistance in Candida auris (C. auris), a species of yeast, and the implications for human health at a seminar hosted by the department of microbiology and immunology Oct. 22.
Fungi cause many common diseases in humans, including yeast infections, athlete’s foot and ringworm. Antifungal resistance occurs when a fungus is no longer susceptible to the medications used to treat it.
Chauhan said that despite the extensive impact of pathogenic fungi on human health, the topic does not receive much attention.
“Fungi, I think, are very important. They impact almost all aspects of human life, from agriculture to biodiversity to food security and of course human health,” Chauhan said. “Unfortunately, fungi and fungal diseases do not receive the attention they deserve.”
Chauhan’s research focused on C. auris, a species of yeast that can cause skin infections and life-threatening bloodstream infections that can spread to vital organs such as the brain. The first human case of C. auris was discovered in 2009, and infections have since spread globally. C. auris spreads through skin-to-skin contact and contact with contaminated surfaces, especially in healthcare facilities like hospitals.
According to Chauhan, the unique qualities of C. auris make it harder to treat than other fungal infections.
“What’s really unique about this fungus is that it adheres to human skin and tends to for a long, long time,“ Chauhan said. “Which means if someone gets colonized by Candida auris, that person can potentially transfer it to another person.”
Compounding the problem, some strains of C. auris have developed resistance to all three classes of antifungal drugs, prompting the Centers for Disease Control and Prevention (CDC) to categorize C. auris as an urgent threat on its annual watchlist of antimicrobial-resistant bacteria and fungi in 2019.
“One thing which is really unique and distinguishes Candida auris is that it happens to be quite resistant to antifungals,” Chauhan said. “Which is a problem because there aren’t many antifungal drugs available.”
Chauhan’s research addresses this growing threat by uncovering how C. auris adheres to human skin and acquires resistance to antifungal drugs. The answer, he found, lies in a gene called HOG1 that encodes a protein that regulates cell responses to a variety of environmental conditions.
After creating two mutant strains of C. auris that produce a deficient HOG1 protein, Chauhan discovered the cells were almost completely killed by the antibiotic Amphotericin B.
“In the presence of the drug the parental isolate grows because it is resistant, but the mutants become almost dead in both strain backgrounds, clearly showing these are important genes in regulating drug resistance,” Chauhan said.
Additionally, HOG1 mutants were less efficient at colonizing skin and establishing colonies in the kidneys and brains of mice.
Kincer Crovetti (GRD ’25), a master’s student in the Biohazardous Threat Agents & Emerging Infectious Diseases program, attended the talk. Crovetti said that Chauhan’s observation of brown C. auris strains, which normally grow white, could indicate increased resilience of C. auris isolates.
“What I thought was really interesting was the phenotypic switching between the white and the brown, especially because we’ve seen a lot of different things with darker fungus being more hardy,” Crovetti told The Hoya.
Stephan Menne, Ph.D., an associate professor in the department of microbiology and immunology, organizes the seminar series, which captures a diverse range of research.
“I usually request speaker suggestions from faculty and especially our Ph.D. students ahead of each semester,” Menne wrote to The Hoya. “I try to cover a broad range of basic and translational research related to infections with pathogens.”
According to Chauhan, it is hypothesized that increasing global temperatures due to climate change could stimulate fungal evolution and allow more species of fungi to survive at human body temperatures.
“Climate change leads to other organisms living on the planet becoming more adept at growing at higher temperatures. Fungi in general are not that good at growing at body temperature, so a rise in temperature allows them to adapt,” Chauhan said.
Crovetti emphasized the importance of building awareness around antifungal resistance, as resistant species of fungi pose an increasing threat to human health.
“If anyone isn’t familiar with this topic, they should at least do a little bit of research into it because it’s going to affect everything at some point,” Crovetti said.
