The bacterial family Pasteurellaceae Pohl 1979 includes opportunistic and primary pathogens mainly associated with warm blooded animals including humans.Classification of the family originally included three genera,Pasteurella,Haemophilus and Actinobacillus.Further taxonomic work,mainly involving phenotypic characterization and molecular classification based on DNA-DNA hybridization and 16S rRNA gene sequence phylogenetic analysis,has resulted in numerous new genera as well as reclassification of some of the original members of Pasteurella,Haemophilus and Actinobacillus,resulting in a total of 22 genera(Christensen et al.2014 a b).Twenty type strains,including six genera of Pasteurellaceae,are available as whole genome sequences and were used for the comparison.In most cases genomes are not closed,but consist of 50-100 contigs.Genome to Genome Distance Calculator(GGDC)(Auch et al.2010)(http://ggdc.dsmz.de/)comparison of these 20 species was performed and index 2 used to construct a neighbor joining phylogenetic tree.The highest distance was obtained between type strains of P.multocida and Aggregatibacter aphrophilus and the lowest between type strains of Haemophilus sputurum and Haemophilus pittmania.The phylogeny showed long terminal branches,since the GGDC comparison includes conserved as well as variable parts of the genomes.Monophyletic relationships found by 16S rRNA gene sequence comparisons were confirmed for members of Actinobacillus(Actinobacillus ureae,Actinobacillus pleuropneumoniae),and Avibacterium(Avibacterium gallinarum and Avibacterium paragallinarum).To a surprise,a divergent relationship was found between P.multocida and P.dagmatis,despite of their monophyly by 16S rRNA gene sequence comparison.Actinobacillus capsulatus was related to A.ureae and A.pleuropneumoniae confirming DNA-DNA reassociation results but opposing the divergence found by 16S rRNA gene sequence phylogeny.The monophyletic group formed between Haemophilus parainfluenzae,Haemophilus pittmania and H.sputurum also corresponded better with DNA-DNA reassociation results than with 16S rRNA gene sequence comparisons.A few whole genome phylogenies have been published for Pasteurellaceae all based on the more conserved genes or predicted proteins,and these studies have shown two major groups of the family,one with Haemophilus,Pasteurella and Aggregatibacter and another with Actinobacillus and Mannheimia(Christensen et al.2014 a).Whole genome sequences of Mannheiraia are not yet available to allow a comparison to the current study.Whole genome sequencing of the remaining around 50 type strains of the family will provide a complete framework for genetic classification both at genus and species level.