The Gram-negative bacterium Haemophilus parasuis is the etiologic agent of Glässer's disease in pigs, and causes significant economic losses to the swine industry. This bacterium has been classified as a member of the family Pasteurellaceae in the genus Haemophilus, but phylogenetic relatedness has not been adequately examined to support this genus classification. Phenotypically, all 38 strains of H. parasuis tested were positive for catalase activity, oxidase activity, V-factor requirement, and acid formation from maltose and d-galactose without gas. All strains were negative for X-factor requirement, formation of indole from tryptophan, urease, l-arabinose, and α-glucosidase activity. To determine whether H. parasuis belongs to one of the current Pasteurellaceae genera 40 H. parasuis genomes, plus those of representative Pasteurellaceae, were subjected to phylogenetic analysis of concatenated, multi-protein alignments. Sequence variation at 16S rRNA and rpoB loci allowed the 15 reference serovars of H. parasuis to be integrated into the whole-genome tree. The phylogenetic analysis showed H. parasuis to be a distinct and tight clade whose sister taxon is the genus Bibersteinia. Within H. parasuis two clades were identified with individual serovars distributed between the two. As a result, H. parasuis was confirmed as a member of the family Pasteurellaceae, but was distinct from other genera in this family. Therefore, we propose the name Glaesserella parasuis, gen. nov., comb. nov. for bacterial strains currently classified as H. parasuis. The reference strain of this species is ATCC 19417 (1374)T, NCTC 4557T, DSM 21448T, CCUG 3712T.
Keywords: Glaesserella parasuis; Haemophilus parasuis; phylogenomic analysis; reclassification; taxonomy.