Nicoletella semolina gen. nov., sp. nov., a New Member of Pasteurellaceae Isolated from Horses with Airway Disease

Abstract

ABSTRACT Gram-negative, nonmotile bacteria that are catalase, oxidase, and urease positive are regularly isolated from the airways of horses with clinical signs of respiratory disease. On the basis of the findings by a polyphasic approach, we propose that these strains be classified as Nicoletella semolina gen. nov, sp. nov., a new member of the family Pasteurellaceae. N. semolina reduces nitrate to nitrite but is otherwise biochemically inert; this includes the lack of an ability to ferment glucose and other sugars. Growth is fastidious, and the isolates have a distinctive colony morphology, with the colonies being dry and waxy and looking like a semolina particle that can be moved around on an agar plate without losing their shape. DNA-DNA hybridization data and multilocus phylogenetic analysis, including 16S rRNA gene (rDNA), rpoB , and infB sequencing, clearly placed N. semolina as a new genus in the family Pasteurellaceae . In all the phylogenetic trees constructed, N. semolina is on a distinct branch displaying ∼5% 16S rDNA, ∼16% rpoB , and ∼20% infB sequence divergence from its nearest relative within the family Pasteurellaceae . High degrees of conservation of the 16S rDNA (99.8%), rpoB (99.6%), and infB (99.7%) sequences exist within the species, indicating that N. semolina isolates not only are phenotypically homogeneous but also are genetically homogeneous. The type strain of N. semolina is CCUG43639 T (DSM16380 T ).