Reassignment of Actinobacillus actinomycetemcomitans to the genus Haemophilus as Haemophilus actinomycetemcomitans comb. nov.

Serological techniques were used to assess the relationships among the following species: Actinobacillus equuli, Actinobacillus lignieresii, Actinobacillus pleuropneumoniae, 'Actinobacillus seminis,' Actinobacillus suis, Actinobacillus actinomycetemcomitans Haemophilus aphrophilus, Haemophilus paraphrophilus, Haemophilus segnis, Haemophilus parainfluenzae, Haemophilus influenzae, Haemophilus parahaemolyticus, Haemophilus aegyptius, and Gardnerella vaginalis. Deoxyribonucleic acid-deoxyribonucleic acid hybridization analyses of A. actinomycetemcomitans, H. segnis, H. aphrophilus, and H. paraphrophilus showed that these four species have measurable deoxyribonucleic acid relatedness of 28% or greater, consistent with their placement in a single genus. These bacterial species also demonstrate common antigens by immunodiffusion. In view of these genetic and serological relationships and previous inclusion of X- and V-factor-independent bacterial species in the genus Haemophilus, reassignment of A. actinomycetemcomitans to the genus as Haemophilus actinomycetemcomitans comb. nov. is proposed.