Reclassification of equine isolates previously reported as Actinobacillus equuli, variants of A. equuli, Actinobacillus suis or Bisgaard taxon 11 and proposal of A. equuli subsp. equuli subsp. nov. and A. equuli subsp. haemolyticus subsp. nov

Abstract

Members of Bisgaard taxon 11 have been isolated from horses. These bacteria are of importance in the veterinary clinic and also to the medical profession, since they may be isolated from infected wounds of humans bitten by horses. Six strains from different continents were identified as taxon 11, with 16S rRNA similarities between 98.0 and 99.7%. A single isolate that represented the so-called (+)L-arabinose-positive Actinobacillus equuli isolated from a diseased foal showed 99.9% 16S rRNA similarity to the type strain of A. equuli. DNA-DNA hybridizations showed that (+)L-arabinose-positive strains of A. equuli represent A. equuli sensu stricto. DNA-DNA hybridizations also showed that A. equuli and Bisgaard taxon 11 represent two genotypes. These genotypes differ with respect to disease pattern and epidemiology. For these reasons, two subspecies of A. equuli are proposed, Actinobacillus equuli subsp. equuli subsp. nov. (type strain NCTC 8529T = ATCC 19392T) and Actinobacillus equuli subsp. haemolyticus subsp. nov. (type strain F 154T = CCUG 19799T = NCTC 13195T).

Reclassification of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov.

“…The explanation for this is probably that 16S rRNA gene sequence comparison is insufficient to resolve all species. This issue is well known for all species (Stackebrandt & Goebel, 1994;Christensen et al, 2002a). A similar comb-like topology has previously been shown for some taxa of Mannheimia and Actinobacillus equuli subsp.…”

“…Key characters for the differentiation of taxa within the genera Avibacterium gen. nov. and Gallibacterium Data based on Blackall & Reid (1982), , Christensen et al (2002aChristensen et al ( , 2003a, Mutters et al (1985a) and this study. All species are Gram-negative and non-motile.…”

Proposed minimal standards for the description of genera, species and subspecies of the Pasteurellaceae

“…The classical method for defining species of the Pasteurellaceae at the genotypic level has been DNA-DNA hybridization. In contrast to most other prokaryotic taxa, where the threshold value for species affiliation is 70 %, species of the Pasteurellaceae have mostly been defined by showing DNA reassociation values of 80-85 % as measured by the spectrophotometric method (Mutters et al, 1989;Christensen et al, 2002Christensen et al, , 2005 Requirements for phenotypic investigations at the species level to document cohesion and separation.Members of a species must share a common set of phenotypic characteristics. In order to separate species, phenotypic characters must also be identified in order to recognize them, and at least two phenotypic differences from existing species should be identified to name a novel species if the study is based on examination of at least five strains of the novel taxon.…”

Fatal Pulmonary Hemorrhage Associated with RTX Toxin-Producing Actinobacillus Equuli Subspecies Haemolyticus Infection in an Adult Horse

“…equuli is associated with septicemia in foals. 6 Pulmonary hemorrhage can have many etiologies with exercise-induced pulmonary hemorrhage, lung abscesses, and pleuropneumonia most commonly recognized in horses. A. equuli subsp.…”

“…equuli. 6 Both hemolytic and nonhemolytic A. equuli strains are part of the normal flora of the oral cavity, the upper respiratory tract, and the gastrointestinal tract of horses. 14 These opportunistic pathogens have been associated in adult horses with pneumonia, pleuropneumonia, arthritis, mastitis, metritis, peritonitis, endocarditis, meningitis, and stillbirth.…”