Intra-familial transmission and distribution of Prevotella intermedia and Prevotella nigrescens.

The periodontal bacteria Prevotella intermedia and Prevotella nigrescens have been recently separated from each other. The purpose of this study was to investigate the distribution and routes of transmission of these bacteria among family members. Seven patients with moderate to severe periodontitis were selected. These probands, their spouses and 14 of their children were investigated. The presence of Pr. intermedia and Pr. nigrescens was determined by culture techniques in pooled subgingival plaque samples, in the saliva, on the tongue, tonsils and buccal mucosa. Differentiation of Pr. intermedia and Pr. nigrescens was performed by enzyme electrophoretic mobility. From all 7 patients, as well as 4 spouses and 3 of the children, Pr. intermedia could be isolated. Pr. nigrescens was found in 2 of the 7 patients, in 5 of the spouses and in 5 of the 6 children aged 5-10 yr. In the 8 children aged 0-4 yr both species were seldom isolated. These data are in accordance with earlier findings that Pr. intermedia is associated with periodontitis and Pr. nigrescens with a relatively healthy periodontal condition. Ribotyping of bacteria was performed by hybridization of HindIII restriction endonuclease digests of chromosomal DNA with ribosomal DNA. Isolates from unrelated individuals always had distinct ribotypes. Indistinguishable ribotypes of Pr. intermedia and Pr. nigrescens were found both among married couples and among parents and children. This indicates that intrafamilial transmission of Pr. intermedia and Pr. nigrescens is possible both between adults and between parents and children.