Bacterial interference in the oral ecology of Actinobacillus actinomycetemcomitans and its relationship to human periodontosis.

The plaque of 7 clinical health subjects was analysed for organisms inhibitory to the growth of A. actinomycetemcomitans strain Y4 on chocolate agar medium. Ten of the 11 sites harboured such organisms which constituted a median of 5.8 per cent of the total cultivable flora. Four to 30 per cent of the isolates in samples from eight sites in periodontitis were also inhibitory to strain Y4. By contrast, 15 of the 16 plaque samples from disease sites of 6 periodontosis (juvenile periodontitis) subjects showed no inhibitors. Four of 5 healthy sites sampled from 3 of the periodontosis subjects showed inhibitors in proportions similar to plaque from healthy subjects. The mother and 3 siblings of a subject with periodontosis lacked inhibitors in one or more plaque samples taken from their 1st molars. This work partially explains the basis for the localized pattern of destruction and the familial tendency of periodontosis.