Over the past few decades, researchers have come to recognize that the plaque-forming microbes in the oral cavity 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 National Institute of Dental and Craniofacial Research (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. Ghannoum, et al reported finding 74 culturable (can be grown in the laboratory) and 11 nonculturable 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. Their article stated, “The oral mycobiome of at least 20% of the enrolled individuals included the 4 most common pathogenic fungi—Candida (present in 75% of the cohort), Aspergilla (35%), Fusarium (30%), and Cryptococcus (20%).” The researchers’ data also exhibited that 60 of the fungal genera identified in their profile are typically noninfectious and are ubiquitous in plants, soil, and air. As the scientists noted, previous attempts to catalogue the oral mycobiome ran into technical problems. Yet their published profile was made possible with a novel pyrosequencing strategy that now opens up the mycobiome for further analysis.
The authors concluded, “The clinical relevance for the presence of a diverse population of fungal species in the oral cavity is unknown. It is possible that the presence of a given fungal isolate (eg, 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.” They continued, “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.”
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