Suppression of penicillin-resistant oral Actinobacillus actinomycetemcomitans with tetracycline. Considerations in endocarditis prophylaxis.

Actinobacillus actinomycetemcomitans is an oral bacterium which is being encountered with increasing frequency in infective endocarditis. This organism occurs in high numbers in periodontitis lesions of patients with localized juvenile periodontitis (periodontosis). It is present infrequently, and only in low numbers in most other individuals. Its common resistance to penicillin, erythromycin and vancomycin represents a clinical problem in patients at risk of developing endocarditis after dental treatment. However, the high activity of tetracyclines against A. actinomycetemcomitans may be useful in prophylactic endocarditis considerations by allowing a suppression of the organism prior to the institution of recommended prophylactic protocols. In this study, we determined the effect of systemic tetracycline-HCl therapy (1 gm/day) on the oral A. actinomycetemcomitans population in five localized juvenile periodontitis patients who were heavily infected with the organism. A. actinomycetemcomitans could not be detected in samples of subgingival and supragingival dental plaque and cheek mucosal surfaces following 14 days of administration of systemic tetracycline. The organism was still undetectable 3 weeks after therapy but it reappeared at a few oral sites at week 8 post-treatment. On the basis of this data, it is proposed that the prophylactic endocarditis therapy of patients with high numbers of penicillin-resistant A. actinomycetemcomitans include a two-stage approach: first, the systemic administration of tetracycline for 14 days, and second, institution of a conventional prophylactic protocol during the time of dental treatment.