The prevalence ofFusobacterium nucleatumsubspecies in the oral cavity stratifies by local health status

Abstract

The ubiquitous inflammophilic pathobiont Fusobacterium nucleatum is widely recognized for its strong association with a variety of human dysbiotic diseases such as periodontitis and oral/extraoral abscesses, as well as multiple types of cancer. F. nucleatum is currently subdivided into four subspecies: F. nucleatum subspecies nucleatum (Fn. nucleatum), animalis (Fn. animalis), polymorphum (Fn. polymorphum), and vincentii/fusiforme (Fn. vincentii). Although these subspecies have been historically considered as functionally interchangeable in the oral cavity, direct clinical evidence is largely lacking for this assertion. Consequently, we assembled a collection of oral clinical specimens to determine whether F. nucleatum subspecies prevalence in the oral cavity stratifies by local oral health status. Patient-matched clinical specimens of both disease-free dental plaque and odontogenic abscess were analyzed with newly developed culture-dependent and culture-independent approaches using 44 and 60 oral biofilm/tooth abscess paired specimens, respectively. Most oral cavities were found to simultaneously harbor multiple F. nucleatum subspecies, with a greater diversity present within dental plaque compared to abscesses. In dental plaque, Fn. polymorphum is clearly the dominant organism, but this changes dramatically within odontogenic abscesses where Fn. animalis is heavily favored over all other fusobacteria. Surprisingly, the most commonly studied F. nucleatum subspecies, Fn. nucleatum, is only a minor constituent in the oral cavity. To gain further insights into the genetic basis for these phenotypes, we subsequently performed pangenome, phylogenetic, and functional enrichment analyses of oral fusobacterial genomes using the Anvi'o platform, which revealed significant genotypic distinctions among F. nucleatum subspecies. Accordingly, our results strongly support a taxonomic reassignment of each F. nucleatum subspecies into distinct Fusobacterium species. Of these, Fn. animalis should be considered as the most clinically relevant at sites of active inflammation, despite being among the least characterized oral fusobacteria.

Fusobacterium nucleatum subsp. polymorphum recovered from malignant and potentially malignant oral disease exhibit heterogeneity in adhesion phenotypes and adhesin gene copy number, shaped by inter-subspecies horizontal gene transfer and recombination-derived mosaicism

“…who recently reported that in healthy dental plaque, F. nucleatum subsp. polymorphum is the dominant subspecies, followed by subspecies animalis and vincentii [5]. Eren et al .…”

“…This distribution is similar to that described by Krieger et al who recently reported that in healthy dental plaque, F. nucleatum subsp. polymorphum is the dominant subspecies, followed by subspecies animalis and vincentii [5]. Eren et al also reported that F. nucleatum subsp.…”

“…nucleatum, polymorphum, animalis and vincentii [2,3]. Based on genome sequencing data, some investigators have suggested classifying these as separate Fusobacterium species [4,5]. Many studies have provided evidence for F. nucleatum's involvement in periodontitis and in adverse pregnancy outcomes, including preterm labour, stillbirth and chorioamnionitis [6,7].…”