Actinomycosis is a chronic localized or hematogenous anaerobic infection caused by Actinomyces israelii. Findings are a local abscess with multiple draining sinuses, a TB-like pneumonitis, and low-grade septicemia. Diagnosis is by the typical appearance plus laboratory identification. Treatment is with a long course of antibiotics and surgery.
The causative organisms, Actinomyces sp (most commonly A. israelii), are often present commensally on the gums, tonsils, and teeth. However, many, if not most, infections are polymicrobial, with other bacteria (oral anaerobes, staphylococci, streptococci, Aggregatibacter [previously Actinobacillus] actinomycetemcomitans, Enterobacteriaceae) frequently cultured from lesions.
Actinomycosis most often occurs in adult males and takes several forms:
Symptoms and Signs
The characteristic lesion is an indurated area of multiple, small, communicating abscesses surrounded by granulation tissue. Lesions tend to form sinus tracts that communicate to the skin and drain a purulent discharge containing “sulfur” granules (rounded or spherical, usually yellowish, and ≤ 1 mm in diameter). Infection spreads to contiguous tissues, but only rarely hematogenously.
The cervicofacial form usually begins as a small, flat, hard swelling, with or without pain, under the oral mucosa or the skin of the neck or as a subperiosteal swelling of the jaw. Subsequently, areas of softening appear and develop into sinuses and fistulas that discharge the characteristic sulfur granules. The cheek, tongue, pharynx, salivary glands, cranial bones, meninges, or brain may be affected, usually by direct extension.
In the abdominal form, the intestines (usually the cecum and appendix) and the peritoneum are infected. Pain, fever, vomiting, diarrhea or constipation, and emaciation are characteristic. One or more abdominal masses develop and cause signs of partial intestinal obstruction. Draining sinuses and intestinal fistulas may develop and extend to the external abdominal wall.
In the localized pelvic form, patients who use an IUD have vaginal discharge and pelvic or lower abdominal pain.
In the thoracic form, lung involvement resembles TB. Extensive invasion may occur before chest pain, fever, and productive cough appear. Perforation of the chest wall, with chronic draining sinuses, may result.
In the generalized form, infection spreads hematogenously to multiple areas, including the skin, vertebral bodies, brain, liver, kidneys, ureters, and, in women, pelvic organs. Diverse symptoms (eg, back pain, headache, abdominal pain) related to these sites may occur.
Diagnosis is suspected clinically and confirmed by identification of A. israelii using microscopy and culture of sputum (ideally obtained endoscopically), pus, or a biopsy specimen. Imaging tests (eg, chest x-ray, abdominal or thoracic CT) are often done depending on findings.
In pus or tissue, the microorganism appears as the distinctive sulfur granules or as tangled masses of branched and unbranched wavy bacterial filaments, pus cells, and debris, surrounded by an outer zone of radiating, club-shaped, hyaline, and refractive filaments that take hematoxylin-eosin stain in tissue but are positive on Gram stain.
Lesions in any location may simulate malignant growths. Lung lesions must be distinguished from those of TB and cancer. Most abdominal lesions occur in the ileocecal region and are difficult to diagnose, except during laparotomy or when draining sinuses appear in the abdominal wall. Aspiration liver biopsy should be avoided because it can cause a persistent sinus.
The disease is slowly progressive. Prognosis relates directly to early diagnosis and is most favorable in the cervicofacial form and progressively worse in the thoracic, abdominal, and generalized forms, especially if the CNS is involved.
Most patients respond to antibiotics, although response is usually slow because of extensive tissue induration and the relatively avascular nature of the lesions. Therefore, treatment must be continued for at least 8 wk and occasionally for ≥ 1 yr, until symptoms and signs have resolved.
High doses of penicillin G (eg, 3 to 5 million units IV q 6 h) are usually effective. Penicillin V 1 g po qid may be substituted after about 2 to 6 wk. Tetracycline 500 mg po q 6 h or doxycycline 100 mg q 12 h may be given instead of penicillin. Minocycline, clindamycin, and erythromycin have also been successful. Antibiotic regimens may be broadened to cover other pathogens cultured from lesions.
Anecdotal reports suggest that hyperbaric O2 therapy is helpful.
Extensive and repeated surgical procedures may be required. Sometimes small abscesses can be aspirated; large ones are drained, and fistulas are excised surgically.
Last full review/revision May 2013 by Joseph R. Lentino, MD, PhD
Content last modified May 2013