Periodontopathic micro-organisms in the rice rat (Oryzomys palustris).

The rice rat spontaneously develops periodontal disease, and this process can be accelerated if the animal is placed on a high sucrose diet. As the aetiological agent(s) is unknown, this study was undertaken to determine the micro-organisms associated with bone loss. Animals at weaning were placed on either a high sucrose diet or on regular rat chow and were sampled periodically for a variety of micro-organisms. Bacteroides spp., spirochetes, and Actinobacillus actinomycetemcomitans were not isolated from any animals, but fusiform-like organisms and Capnocytophaga spp. were isolated occasionally. An unidentified organism which had characteristics of both A. actinomycetemcomitans and Haemophilus aphrophilus was isolated from all animals at every sampling. Whether this organism is the primary aetiological agent of periodontal disease in the rice rat remains to be determined. Over the 12 week experimental period the animals on the high sucrose diet had significantly more exposed root surface than animals on regular rat chow.