The Role ofEubacteriumSpecies in Periodontal Disease and Other Oral Infections

Abstract

Periodontal disease has been traditionally associated with an anaerobic gram-negative microbiota. However, improvements in sampling handling and culture media have revealed that gram-positive anaerobes belonging to the genus Eubacterium can make up around half of the microbiota in advanced disease. The asaccharolytic species E. brachy, E. nodatum, E. saphenum and E. timidum show significant associations with severe periodontal disease, but are only rarely found in oral health. Antibodies to E. brachy and E. timidum are raised in patients with periodontal disease compared with healthy controls. Studies of the genus are hampered by the poor and slow growth of the majority of species and the indifferent taxonomy of the group. It is estimated that there are at least 20 un-named taxa. 16S ribosomal RNA sequencing has revealed that the oral asaccharolytic Eubacterium species are closely related to the genera Clostridium and Peptostreptococcus and exhibit three distinct lines of descent. Virulence factors produced by these organisms are as yet unknown although one unnamed taxon which is strongly associated with dento-alveolar abscesses has been established in continuous culture and has been shown to exhibit a wide range of aminopeptidase activity.