Actinobacillus actinomycetemcomitans in Human Periodontal Disease: Prevalence in Patient Groups and Distribution of Biotypes and Serotypes Within Families

Abstract

Actinobacillus actinomycetemcomitans is a Gram‐negative oral bacterium which has been implicated in the etiology of localized juvenile periodontitis. In this study, 403 subjects from four study groups were examined for A actinomycetemcomitans in subgingival dental plaque. Samples pooled from at least six periodontal sites were included from each subject. A actinomycetemcomitans was detected in 28 of 29 localized juvenile periodontitis patients but in only 15% of the other subjects including 28 of 134 adult periodontitis patients, 24 of 142 periodontally healthy subjects and 5 of 98 insulin dependent juvenile diabetics with varying degrees of gingivitis. A actinomycetemcomitans isolates from members of five families with localized juvenile periodontitis patients were biotyped on the basis of variable fermentation of dextrin, maltose, mannitol and xylose and serotyped by indirect immunofluorescence using serotype specific rabbit antisera. Individuals within a family all harbored A actinomycetemcomitans of the same biotype and serotype. However, even in families with individuals heavily infected with A actinomycetemcomitans, some family members did not appear to be infected with the organism. The apparent poor transmissibility of A actinomycetemcomitans between individuals may, in part, explain the overall low prevalence of localized juvenile periodontitis and the familial pattern of the disease. The high prevalence of A actinomycetemcomitans in the subgingival plaque of localized juvenile periodontitis patients, compared to the much lower prevalence in other patient groups, supports the hypothesis that A actinomycetemcomitans is an etiologic agent in this periodontal disease. The reason(s) an infection with A actinomycetemcomitans may result only in a localized type of periodontal breakdown is not known; this paper presents some hypotheses which may explain this characteristic clinical feature.