ACTINOMYCOSIS

Document last modified: 070104  CJS, GG

Actinomycosis is from Greek aktis, (genitive aktinos) meaning a ray (radiation) and mykes meaning fungus.

Definition: Actinomycosis is a subacute to chronic suppurative infection caused by certain fungus-like bacteria of the genus Actinomyces; of the family Actinomycetaceae, order Actinomycetales. It is not held as contagious.

Actinomycosis was described as a clinical entity over 100 years ago.

Epidemiology: Not uncommon, but the incidence - which has decreased markedly since the introduction of antibiotics - remains unclear. The disorder is about three times as common in men as in women, and most common during the middle decades; and in the developing part of the world.

Aetiology - Pathogenesis - Associated Condition(s): The Gram-positive, facultative anaerobic Actinomyces israelii - also called ray fungus; a non-acid fast rod of serologic group D - is often normally present in the oral cavity, and the usual pathogen in man. The disease may also be caused by A. naeslundii of serologic group A, A. viscosus of serologic group F, A. meyeri, A. odontolyticus of serologic group E,  Actinomyces gerencseriae, or Propionibacterium propionicum (formerly Arachnia propionica); all of which are also normally present in the mouth or the gastrointestinal tract of man. Infection and disease occurs when the protective barriers are broken, for instance by trauma. The causative microorganisms grow within the tissue as grossly visible, yellow clusters, often referred to as 'sulphur granules'.

Most actinomycotic infections are, furthermore, polymicrobial, harbouring Actinobacillus actinomycetemcomitans, Eikenella corrodens, Enterobacteria and species of Fusobacterium, Bacteroides, Capnocytophaga, Staphylococcus, and Streptococcus. The influence of these species is unknown, but it seems that they act as predisposing factors by lowering the host defence.

The disease seen in cattle is caused by A. bovis - a non-acidfast facultative anaerobic species of serologic group B.

Clinical features:  Actinomycosis is classically divided into particular forms which follow the port of entry of the causative microorganisms. In man, it is most often seen in a cervicofacial location; in particular in relation to the jaws and to an antecedent, local lesion such as a dental/periodontal infection or tooth extraction. A typical case is illustrated here with its port of entry (Fig. 1), the sulphur granules (Fig. 2) and several ports of exit (Fig. 3) of different age.

The following are the classical manifestations, but virtually any organ may be affected:

• Cervicofacial actinomycosis - the most common form, more than 50% of the cases - usually presents as a red or purplish, somewhat indurated subcutaneous mass; typically in the submandibular area or in the anterior cervical triangle near the angle of the mandible. Tenderness is slight or absent. The swelling corresponds to a burrowing sinus of infection, which will eventually break through the skin and give rise to an open fistula; emptying a purulent material containing the 'sulphur granules' - i.e. colonies of  micro-organisms. The swelling is often accompanied by trismus, and healing occurs with fibrosis.
  Actinomycosis may also be seen to affect the tonsils, tongue, cheek and lips; the implantation of the micro-organisms then often being associated with some kind of traumatic wound.
  A particular intraoral manifestation  - which affects the marginal gingiva and renders it erythematous and painful; and which may apparently exist without any other cardinal signs of actinomycosis - has been given the label Actinomycotic gingivitis. This condition should be held in mind in any case of intractable periodontal lesions.
• Pulmonar or thoracic actinomycosis presents in the lungs, and is accompanied by fever and general malaise, cough and purulent sputum. Cutaneous sinuses may form.
• Abdominal actinomycosis may cause pain and a palpable mass in the abdomen. Pelvic actinomycosis is commonly associated with intrauterine contraceptive devices.

Microscopy: The histopathological lesion is usually pathognomonic. In biopsies, which are rarely needed, there is a central area with numerous 'sulphur granules' (Fig. 2, Fig. 4 a, b, c, d), surrounded by a granulomatous connective tissue harbouring polymorphonuclear granulocytes and histiocytes. Later stages show a total tissue breakdown - necrosis - and the formation of abscesses in the centre of the lesion; the pus eventually forming large sinuses with surrounding connective tissue fibrosis, and which empty through cutaneous fistulas with walls covered by ingrown squamous cell epithelium.

Diagnostic criteria: Actinomycosis has been said to be .. "The most misdiagnosed and missed disease". Criteria will rest upon clinical history and appearance, smears of discharged - or fine-needle aspirated - material showing 'sulphur granules' directly or colonies of actinomyces upon anaerobic culture. Microbiological tests are difficult to interpret since most lesions have been treated with antibiotics prior to the test. Microbiological samples should preferably be transported in an anaerobic transport device.

Differential diagnosis: Uncompromised dental or periodontal abscesses, tuberculosis, nocardiosis; other infections. Neoplasms.

Treatment: The initial presentation may call for incision and drainage, and / or surgical curettage. The infection itself is cured with prolonged antibiotic treatment: penicillin G or V, eventually combined with metronidazole or tetracycline, for months; and at least 2 weeks after clinical cure.

Prognosis - Natural history/Outcome upon treatment: Actinomycosis is a chronic disorder, and sinuses may heal while new ones form if there is no treatment. Prolonged treatment with antibiotics is effective.

Caveats for Dental/Oral Care: 

Nagler RM, Ben-Arieh Y, Laufer D. Case report of regional alveolar bone actinomycosis: a juvenile periodontitis-like lesion. J Periodontol 2000;71:825-9. Medline abstract

Search PubMed for cervicofacial actinomycosis.