Scientists Profile Oral Mycobiome

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.”