Recalled Yogurt Harbored Harmful Fungus

Soo Chan Lee, PhD Senior Research Associate, Center for Microbial Pathogenesis, Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, N.C. 27710 MedicalResearch.com Interview with:
Soo Chan Lee, PhD
Senior Research Associate,
Center for Microbial Pathogenesis,
Department of Molecular Genetics and Microbiology,
Duke University Medical Center,
Durham, N.C. 27710

Medical Research: What are the main findings of the study?

Dr. Soo Chan Lee: Mucor circinelloides strain isolated from recalled Chobani yogurt was found to be the most virulent subspecies M. circinelloides forma circinelloides that is commonly associated with human infections. When mice were infected with this fungus through the tail-vein, 80% mortality was observed 5 days post infection. When mice were fed with spores, the fungus survived passage through the GI tract as many as 10 days, indicating the fungus can colonize to cause infections. Whole genome sequence analysis revealed the possibility that this fungus could produce harmful secondary metabolites that are unknown in this fungal species.

Medical Research: Were any of the findings unexpected?

Dr. Soo Chan Lee: Mucor circinelloides is already known as one of the causal agents for mucormycosis, which is rare but aggressive with high mortality in case of disseminated infections. So virulence of the fungus in mouse is kind of expected.

However, one interesting finding was that the fungus survived the passage through the mouse GI tract.

Dr. Soo Chan Lee: When people think about food-borne pathogens, normally they list bacteria, viruses, and parasites. Fungal pathogens are not considered food-borne pathogens. However, this incidence (Chobani yogurt recalled after customer complaints of discomfort and their products were contaminated by Mucor circinelloides) indicates that we need to pay more attention to fungi. Fungal pathogens can threaten our health systems as food-borne pathogens.

The immunocompromised population is increasing as a result of HIV-AIDS infection, diabetes, and other medical conditions. Elderly populations are increasing too. Those people are especially susceptible to fungal infections. As mentioned above, specific attention needs to be given to fungi. It may be time to consider developing sound regulations about fungi in food products and factories that manufacture them.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Soo Chan Lee: It is less evident so far that this fungus really causes food-borne illness through infection or production of toxic compounds. Our study evaluated the potential risks of this fungal infection. Further study could include examination of whether this fungus can produce any secondary metabolites because its genome tells us it would be possible.

Citation:

Analysis of a foodborne fungal pathogen outbreak: virulence and genome of a Mucor circinelloides isolate from yogurt,” Soo Chan Lee, R. Blake Billmyre, Alicia Li, Sandra Carson, Sean M. Sykes, Eun Young Huh, Piotr Mieczkowski, Dennis C. Ko, Christina A. Cuomo, and Joseph Heitman. mBio, July 8, 2014. DOI:10.1128/mBio.01390-14