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Actinomycosis is a slowly progressive suppurative infection characterized by fistula formation. A number of gram positive, non spore forming bacteria from the genus Actinomyces are the etiologic agents.1-3 It is encountered worldwide in three main clinical forms: cervicofacial, thoracic, and abdominal.1 Metastatic lesions to other sites are also reported. With appropriate therapy, most patients with cervicofacial or abdominal infection recover completely.

Etiologic Agent and Pathogenesis

Actinomyces species are part of the normal flora of the human gastrointestinal tract. They do not inhabit the female genitourinary tract in the absence of an intrauterine device (IUD).4 Actinomycosis is not considered an opportunistic or communicable disease. Although uncommon in children, actinomycosis has been reported in infancy.5 The disease is not related to occupation, season, or race.

A. israelii, the species that most commonly produces human disease, is part of normal oral flora. A. viscosus, A. naeslundii, A. odontolyticus, A. meyeri, and Propionibacterium (Arachnia) propionica are also established etiologic agents.1-3 Cervicofacial and abdominal infections are thought to occur when these organisms are traumatically introduced into tissues.6 Predisposing factors for actinomycosis include gingivitis, gingival trauma, dental procedures, tooth-related infections, diabetes mellitus, malnutrition, immunosuppression, and local tissue damage from different causes including trauma, radiation, and neoplasia as well as the use of an IUD.7,8 It has been shown than Actinomyces sp require the presence of other bacteria to multiply. Thus, actinomycosis is frequently polymicrobial in nature, and concomitant bacterial species such as Eikenella corrodens, Actinobacillus actinomycetemcomitans, Fusobacterium, Capnocytophaga, Staphylococcus, microaerophilic streptococci, and Enterobacteriaceae are often isolated from actinomycotic lesions.9-11Actinomyces sp require an anaerobic or microaerophilic environment for growth and demonstrate gram positive branching filaments, often appearing as beaded filaments.

A pivotal step in pathogenesis is the disruption of mucosal barriers, allowing access of these organisms to deep tissue. Thus, oral and cervicofacial disease are associated with dental procedures, trauma, and oral surgery.7 However, actinomycotic infections are infrequent, and some cases of actinomycosis may even develop after minor trauma such as eruption of a normal tooth.7 In fact, actinomycosis may not develop after major oral trauma or surgery. This indicates that oral or mucosal trauma alone is not the only factor responsible for actinomycotic infections. Other conditions may be required for Actinomyces sp to proliferate and establish an infection. These include the duration and severity of trauma that induce the microaerophilic environment as well as the synergistic effect of other bacteria.12 Abdominal infection is preceded by gastrointestinal surgery, appendicitis, diverticulitis, traumatic injury secondary to gunshot or knife wounds, or foreign bodies such as fish bones.11 Pelvic actinomycosis is associated with intrauterine devices.8 Pulmonary disease is believed to be secondary to aspiration.1 Once inoculated, the organism replicates and spreads contiguously in a slow and progressive manner with little respect for tissue planes. ...

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