A genome-led study on the pathogenesis of Fusobacterium necrophorum infections.

Fusobacterium necrophorum causes a range of mild to life threatening infections and there is uncertainty in terms of diagnosis and treatment due to the lack of knowledge on their pathogenic mechanisms. This study characterised genomes of F. necrophorum to compare their virulence factors and investigate potential infection markers. 27 isolates of F. necrophorum from patients with pharyngotonsillitis were subjected to whole genome sequencing and compared with 42 genomes published in the NCBI database. Phylogenomics, pangemome, pan-GWAS and virulome were analysed to study strain variations with reference to virulence factors. Core genome based phylogenomic tree exhibited three clades of which Clade A belonged to F. necrophorum subsp necrophorum, clades B and C were F. necrophorum subsp funduliforme. Pan-GWAS and Pan-Virulome suggest some marker genes associated with clinical sources of isolation that needs further validation. Our study highlights some interesting features of the pathogenesis of F. necrophorum infections. Although the animal isolate genomes had some marker genes, the genomes of human isolates did not exhibit clear correlation to their clinical sources of isolation. This prompts to think of other mechanisms such as co-infections or host factors that can be involved in the pathogenesis.