Initial identification of genomic islands in Taylorella equigenitalis and Taylorella asinigenitalis and their distribution in isolates from around the world

Taylorella equigenitalis, the causative agent of contagious equine metritis (CEM), is endemic in several countries throughout the world and impacts the global movement of horses. It presents with symptoms ranging from non-clinical to endometritis, vaginitis, and acute infertility in females while males remain asymptomatic. Studies of the disease have focused primarily on understanding pathology, transmission dynamics, diagnostics, and phenotypic and genotypic characteristics. The goal of this study was to establish a more comprehensive global phylogenetic structure and generate reference-quality genomes for each major clade of the tree where such data were absent. Seven of these genomes along with 44 other publicly available genome assemblies, including Taylorella asinigenitalis, were then used to predict genomic islands. Exploration of the NCBI annotations in the genomic islands indicate links to virulence and ecological fitness. An additional 97 T. equigenitalis and 48 T. asinigenitalis short-read isolates from this study and 215 publicly available genomes were used to examine distribution of each genomic island across the phylogenetic tree for evidence of horizontal movement. The stability of these genomic islands in their natural environment was evaluated utilizing 141 isolates recovered from a recent CEM outbreak in the United States. The results obtained in this study demonstrate mobile genomic islands in T. equigenitalis genomes, sites of concern for their contribution to the potential virulence of the organism.