During a screening study for
Pasteurella multocida
in two unrelated flocks of Muscovy ducks pharyngeal and cloacal swabs were collected. A total of 59
Pasteurellaceae
-like isolates sharing the same colony morphology were subcultured and subsequently characterized. Colonies on bovine blood agar were nonhaemolytic, regular, circular, slightly raised, shiny, intransparent with an entire margin, greyish and had an unguent-like consistency. Isolate AT1T was characterized by 16S rRNA gene sequencing and showed the highest similarity of 96.1 % to the type strain of
Mannheimia caviae
and 96.0 % to the type strain of
Mannheimia bovis
, respectively. In addition, rpoB and recN gene sequences also showed the highest similarity to the genus
Mannheimia
. The phylogenetic comparison of concatenated conserved protein sequences also showed a unique position of AT1T compared to other species of
Mannheimia
. Full phenotypic characterization of the isolates showed that between two (
Mannheimia ruminalis
) and 10 (
Mannheimia glucosida
) phenotypic characteristics separate the taxon isolated from Muscovy ducks from the accepted species of
Mannheimia
. Whole genomic sequences of two strains analysed by the type strain genome server showed the highest similarity of 24.9 % to the genome of the type strain of
Pasteurella multocida
and 23.0 % to the genome of the type strain of
Mannheimia haemolytica
. The species Mannheimia cairinae sp. nov. is proposed based on the phenotypic and genotypic similarity to
Mannheimia
as well as differences to the other validly published species of the genus. The leukotoxin protein was not predicted in the genome of AT1T. The G+C content of the type strain of M. cairinae sp. nov., AT1T (=CCUG 76754T=DSM 115341T) is 37.99 mol%, calculated from the whole genome. The investigation further proposes that
Mannheimia ovis
is reclassified as a later heterotypic synonym of
Mannheimia pernigra
, since
M. ovis
and
M. pernigra
are closely genetically related, and
M. pernigra
was validly published before
M. ovis
.