Transfer of Haemophilus pleuropneumoniae and the Pasteurella haemolytica-Like Organism Causing Porcine Necrotic Pleuropneumonia to the Genus Actinobacillus (Actinobacillus pleuropneumoniae comb. nov.) on the Basis of Phenotypic and Deoxyribonucleic Acid Relatedness

The Pasteurella-like organism of porcine necrotizing pleuropneumonia described by Bertschinger and Seifert in 1978 was shown to be phenotypically similar to the V factor-requiring strains hitherto classified as Haemophilus pleuropneumoniae (Matthews and Pattison 1961) Shope 1964. Deoxyribonucleic acid-deoxyribonucleic acid hybridization experiments in which the optical method was used yielded 91% binding of the genomes of the type and reference strains of these two taxa, thus indicating that they belong to the same species. The levels of deoxyribonucleic acid binding between these strains and the type strain of Haemophilus influenzae indicated no measurable relatedness. Therefore, these organisms do not belong to the genus Haemophilus sensu stricto. On the other hand, they are closely related to Actinobacillus lignieresii, as determined by both phenotypic characteristics and deoxyribonucleic acid base sequence relatedness (72 to 75% binding). To take into account the different host ranges of these organisms, we propose to classify them as a species distinct from, but closely related to, A. lignieresii, under the new combination Actinobacillus pleuropneumoniae. The emended species A. pleuropneumoniae is composed of V factor-requiring and V factor-independent biovars. The type strain (strain Shope 4047 [= CCM 5869 = ATCC 27088]) requires V factor; the V factor-independent biovar is represented by strain Bertschinger 2008/76 (= Frederiksen P 597 = HIM 677-3/4).