In recent years we received an increase of submission of haemophilic bacteria sourced from the respiratory tract of pigs to our reference laboratory for confirmation of identification. Due to the lack of discriminatory power of the routine 16S rDNA sequencing for closely related species within the Pasteurellaceae family, we analysed the 36 field isolates by using multi-locus sequence analysis (MLSA) of three housekeeping genes; recN, rpoA and thdF.
Geneious version 8.0.5 was used for aligning and similarity index calculation of the amplified genes to those from the type strains within the genera Actinobacillus and Glaesserella.
Among these 36 isolates a new species, consisting of 17 isolates, was identified with a genome similarity index of 0.56 to the closest related type strains – Glaesserella parasuis and A. indolicus. The type strains of Glaesserella parasuis and A. indolicus formed a group with nine isolates. A further seven isolates did not fit into a group due to lack of congruence of the thdF gene phylogeny with recN and rpoA and their identity remains uncertain.
The 17 isolates of the potentially new species were further analysed using whole genome phylogeny. The candidate type strain (HS4635T) of the potential new species shared 30.9% DNA-DNA homology with Glaesserella parasuis. The most outstanding biochemical difference between this new species with other members of the genera Actinobacillus and Glaesserella is the capacity to produce cytochrome C oxidase and indole, while lacking the capacity to produce catalase or urease. Like Glaesserella parasuis and some members of the genus Actinobacillus, this newly identified Gram-negative bacteria is satellitic on blood agar. Other key properties are acid formation from (-)-D-arabinose, (+)-D-galactose, (+)-D-maltose and trehalose, a failure to produce acid from (-)-D-mannitol and the production of b-galactosidase but not a-fucosidase. This new species is in the process of being officially named as Glaesserella australis sp. nov.