Genetic analysis of Ornithobacterium rhinotracheale isolates: an Australian perspective

This study examined the genetic diversity in a collection of field isolates of Ornithobacterium rhinotracheale and compared that with the diversity in the serovars A-D and F-I reference strains and available whole genome sequences. Phylogenetic analysis of the 16S rRNA gene of the nine Australian isolates and twelve sequences of overseas isolates resulted in six clusters with the Australian isolates not closely related to either the type strain or the serovar reference strains. The suitability of low-cost finger printing techniques, ERIC-PCR and rep-PCR, when applied to O. rhinotracheale were also evaluated. The fingerprints generated through ERIC-PCR were more informative and this method subsequently used to examine the genetic diversity of the isolates and the reference strains. The ERIC-PCR patterns confirmed the isolates and strains were quite diverse, with 15 different patterns detected. These results suggested that the Australian isolates were genetically distinct from the overseas strains, consistent with the genetic distinction observed in the phylogenetic study. Whole genome sequences of the Australian isolate BR2963 and the 15 genomes identified as O. rhinotracheale in the Genome Taxonomy Database confirmed that serovars F, K and M form a cluster distinct from other O. rhinotracheale and probably represent a distinct species within the genus Ornithobacterium. Additionally, the Australian isolate BR2963 had an average nucleotide identity level with the O. rhinotracheale type strain (DSM15997^T) below the accepted 95% threshold for species suggesting that the isolate is a member of the genus Ornithobacterium but not within the species rhinotracheale.