Periapical actinomycosis involving Actinomyces israelii

Actinomyces organisms are common commensalsof the oral cavity, but the disease actinomycosis is uncommon, and local predisposing factors are thought to be important in the etiology. Although it has been shown that organisms are commonly present in infected root canals, infection in the periapical tissues is unusual. When this occurs, diagnosis has been made by recognition of colonies in histopathological specimens. A case is presented in which recognition was made by microbiological means, enabling determination of the species of organism involved. The organism in this case, Actinomyces israelii, is that which is reported to be commonly involved in other forms of actinomycosis.