Actinobacillus actinomycetemcomitans infection in the oral cavity.

An abscess that developed following the extraction of periodontally involved teeth persisted after surgical drainage and ampicillin therapy. Subsequent culture of pus from this abscess gave a pure growth of Actinobacillus actinomycetemcomitans which was resistant to ampicillin. Surgical drainage and the use of appropriate antibiotic therapy cleared the infection. The identification of A. actinomycetemcomitans and the types of infection it causes are described. The probable mechanism of infection by the bacterium is discussed. A case that illustrates the importance of the microbiologic examination of pus from dental abscesses is reported.