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Scientists Profile Oral Mycobiome

January 26, 2010

Distribution of fungi in oral rinse samples from 20 healthy individualsIn his 1966 book, The Psychology of Science, Abraham Maslow famously declared, “I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.” But these days when more research tools than ever are at hand in the laboratory, it’s tempting to flip Maslow’s words. If all you see are nails, the only tool required is a hammer. Or, applying these words directly to oral health and the decades-old study of the plaque-forming microbes that inhabit our mouths: If all you see are bacteria, the only tool required is better anti-bacterial treatments.

Over the past few decades, however, researchers have come to recognize that these plaque-forming microbes live as complex microbial communities. In addition to exploring the symbiotic interactions of oral bacteria, they also frequently note the presence of the other microbial inhabitants of the mouth, such as Archaea and fungi. The problem is this recognition, particularly of the oral fungi, tends to be more conceptual than experiential. That’s because few oral fungi actually have been isolated and documented in the scientific literature, leaving many to believe that only a few species exist in the mouth.

As published online in January in the journal PLoS Pathogens, a team of NIDCR grantees and their colleagues provide for the first time a comprehensive snapshot of the oral fungal mycobiome, or all of the fungal organisms - and their collective set of genes – that are present in the human mouth. The researchers reported finding 74 culturable (can be grown in the laboratory) and 11 non-culturable fungal genera collectively in dental plaque samples from 20 healthy individuals. This breaks down to 101 distinct species, a clear indication that the oral mycobiome is not limited to a few species. “The oral mycobiome of at least 20% of the enrolled individuals included the four most common pathogenic fungi - Candida (present in 75% of the cohort), Aspergilla (35%), Fusarium (30%), and Cryptococus (20%).” Their data also showed that 60 of the fungal genera identified in their profile are typically non infectious and are ubiquitous in plants, soil, and air. As the scientists noted, previous attempts to catalogue the oral mycobiome ran into technical problems. But their published profile was made possible with a novel pyrosequencing strategy that now opens up the mycobiome for further analysis.

“The clinical relevance for the presence of a diverse population of fungal species in the oral cavity is unknown,” the authors concluded. “It is possible that the presence of a given fungal isolate (e.g. Candida, Aspergilla, Cryptococcus, and Fusarium) in an individual could be the first step in predisposing the host to opportunistic infections. In this regard, oral Candida colonization has been known to be a risk factor for Candida infections in immunocompromised patients. Understanding the relationships between different fungal species as well as between fungi and other members of the oral microbiome will shed light on the pathogenicity of these organisms and may lead to the discovery of novel therapeutic approaches for the prevention and treatment of oral complications.” 

  • Characterization of the Oral Fungal Microbiome (Mycobiome) in Healthy Individuals, Ghannoum MA et al. PLoS Pathogens 2010, January; 8 (6), e10000713. 



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This page last updated: February 26, 2014