Many wound infections are caused by anaerobes other than Clostridia. The main offenders are members of the normal flora of the mouth and intestine. Actinomycosis is not a mycosis since it is not caused by a fungus, but its name persists from when it was thought to be a fungal disease.
Actinomycosis is characterized by slowly progressive, sometimes painful swellings under the skin that eventually open and chronically drain pus. The openings usually heal, only to reappear at the same or nearby areas days or weeks later. Most cases involve the area of the jaw and neck; the resulting scars and swellings gave rise to the popular name "lumpy jaw" (figure 27.13). In other cases the recurrent swellings and drainage develops on the chest or abdominal wall, or in the genital tract of women.
Most cases of actinomycosis are caused by Actinomyces israelii, a Gram-positive, filamentous, branching, anaerobic bacterium that grows slowly on laboratory media. A number of similar species can cause the disease in animals and humans.
Actinomyces israelii cannot penetrate the normal mucosa, but it can establish an infection in association with other organisms if introduced into tissue by wounds. The infectious process is characterized by cycles of abscess formation, scarring, and formation of sinus tracts, or passageways that generally ignore tissue boundaries. The disease usually progresses to the skin where pus is discharged, but occasionally it penetrates into bone, or into the central nervous system. In the tissue, A. israelii grows as dense yellowish colonies called sulfur granules (figure 27.14) because they are the color and size of particles of elemental sulfur. Since other more rapidly growing bacteria are invariably pre sent, finding sulfur granules in the sinus drainage is a great aid in establishing the diagnosis. Almost half of the cases originate from wounds in the mouth, the remainder from the lung, intestine, or vagina. The detailed mechanisms by which the organism produces the disease have not yet been established.
Actinomyces israelii can be part of the normal flora of the mucosal surfaces of the mouth, upper respiratory tract, intestine, and sometimes the vagina. It is common in the gingival crevice, particularly with poor dental care. Pelvic actinomycosis can complicate use of intrauterine contraceptive devices (IUDs). Other species of Actinomyces responsible for actinomycosis of dogs, cattle, sheep, pigs, and other animals generally do not cause human disease. The disease is sporadic and is not transmitted person to person. ■ gingival crevice, p. 599
There are no proven preventive measures. Actinomycosis responds to treatment with a number of antibacterial medications, including penicillin and tetracycline. To be successful, however, treatment must be given over weeks or months. This need for prolonged therapy probably is due to the slow growth of the organisms and their tendency to grow in dense colonies. The main features of actinomycosis are presented in table
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