Deoxyribonucleic Acid Relatedness Among Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, and Other Actinobacillus Species

Abstract

The relationship among 22 strains of Actinobacillus actinomycetemcomitans, 3 strains of Haemophilus aphrophilus, 1 reference strain of Actinobacillus ligniere- sii, and the type strain of Actinobacillus equuli were assessed by deoxyribonucleic acid (DNA)-DNA hybridizations on membrane filters. We found that the A. actinomycetemcomitans strains formed a homogeneous group that was distinct from H. aphrophilus and the other Actinobacillus species. There was about 40% hybridization between H. aphrophilus DNA and A. actinomycetemcomitans DNA, indicating some similarity, but A. lignieresii and A. equuli DNAs hybrid- ized much less (never more than 20%) with A. actinomycetemcomitans DNA. Interest in Actinobacillus actinomycetemco- mitans has increased recently since this bacteri- um has been found to be associated with human periodontal disease, especially those forms of periodontal disease that seem to progress rapid- ly (15). This organism can also be found in the mouths of subjects without periodontal disease. In addition, A. actinomycetemcornitans is fre- quently associated with actinomycosis (15). Oral isolates of this species show some degree of heterogeneity in serology (13) and sugar fer- mentation patterns (12), although the overall characteristics of 136 strains were recently shown to be quite uniform (14). The same study pointed out the characteristics by which A.