Intrafamilial transmission of Actinobacillus actinomycetemcomitans.

Cross-sectional studies have shown that Actinobacillus actinomycetemcomitans is a frequent member of the oral flora in children with primary teeth. The purpose of the present study was to obtain information of the transmission of A. actinomycetemcomitans. Three types of families were studied for the prevalence and serotype distribution of A. actinomycetemcomitans. First, families whose periodontally healthy child member harbored A. actinomycetemcomitans; second, families of periodontally healthy children who did not harbor A. actinomycetemcomitans; third, families whose adult member harbored A. actinomycetemcomitans and had been referred to treatment for severe periodontitis. As a whole the study included 23 families. All the family members were invited for the examination. The final study population consisted of 38 children and 32 adults. The results showed that when a child was positive for A. actinomycetemcomitans, either the mother or the father was also positive with one exception, whereas when the adult member harbored A. actinomycetemcomitans, the children were infected in only 2 of the 9 families. Using immunodiffusion technique it was found that the child always harbored the same serotype of A. actinomycetemcomitans as the parent. In conclusion, the results suggest the intrafamilial transmittance of A. actinomycetemcomitans.