In September of 2013, customers of Chobani brand Greek yogurt complained of gastrointestinal problems after consuming products manufactured in the company's Idaho plant. The company issued a recall and claimed that the fungal contaminant Murcor circinelloides was only a potential danger to immunocompromised individuals.

Yet complaints of severe GI discomfort continued from otherwise healthy customers and researchers began to question the fungus and its ability to cause harm in healthy humans.  Resulting research has found that this fungus is not harmless after all, but a strain with the ability to cause disease. 

In the study, the researchers isolated a strain of the fungus from a yogurt container that was subject to recall. Using a technique known as multi-locus sequence typing (MLST), they identified the strain as Mucor circinelloides f. circinelloides (Mcc). Unlike other strains of the fungus, that particular subspecies is commonly associated with human infections.

Mucho is sexually compatible with an M. circinelloides f. circinelloides isolate. Zygospore formation between Mucho and (−) NRRL3614 was observed, whereas Mucho did not mate with (+) NRRL3615 (data not shown). The results indicate that Mucho is the (+) mating type. Its mating ability with the other M. circinelloides f. circinelloides isolate also supports that Mucho is M. circinelloides f. circinelloides. Scale is 100 µm. Credit: 

Whole-genome sequence analysis of the yogurt isolate confirmed it as being closely related to Mcc and also revealed the possibility that this fungus could produce harmful metabolites that were previously unknown in this species.

The researchers then tested the strain on mice, where the fungus showed an ability to cause lethal infections when the fungal spores were injected into the bloodstream as well as to survive passage through the GI tract when the spores were ingested orally. 

Maybe accept science more and you will put people at risk less. Image link: Dr. Piper Klemm

"When people think about food-borne pathogens, normally they list bacteria, viruses, and maybe parasites. Fungal pathogens are not considered as food-borne pathogens. However, this incidence indicates that we need to pay more attention to fungi. Fungal pathogens can threaten our health systems as food-borne pathogens," says co-author Soo Chan Lee of Duke University.

Citation: 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 , 'Analysis of a Food-Borne Fungal Pathogen Outbreak: Virulence and Genome of a Mucor circinelloides Isolate from Yogurt', mBio 5:4 July/August 2014; doi:10.1128/mBio.01390-1. Source: American Society for Microbiology