Actinomycosis (Actinomyces Infection)

Actinomycosis PHIL 2856 lores[1]

Actinomycosis is an infectious bacterial disease, frequently observed on the neck and face, that leads to the formation of abscesses and sinus tracts.


Actinomyces colonies consist of pus-filled cavities (abscesses), which form an interconnected network, encased by granulomatous material. Sinus tracts are often formed, connecting the lesion to the skin; they tend to produce a sulfur-like granulomatous material of yellowish color. The initial infection site can be anywhere in the body, with the most frequent location being the head (cervicofacial actinomycosis); the bacteria disseminate to adjacent regions by local invasion and very rarely via the bloodstream.

In cervicofacial actinomycosis, the initial infection site is found in the skin epidermis, the oral mucosa or the jaw subperiosteal region. The lesions are limited in size, rigid, swollen and may be painful. Sinus tracts are formed as the condition progresses, which produce the typical yellowish granulomatous material. Finally, actinomyces may infest a plethora of adjacent locations such as the meninges, tongue, skull bones and brain, by local invasion [9].

The second most common clinical type of actinomycosis is its abdominal counterpart. The intestine and peritoneum are the predominant sites of initial infection [10]. The condition becomes clinically alarming, with the patient exhibiting fever, diarrhea, nausea, vomiting and malnutrition, alongside lesions that grow intrabdominally, causing intestinal obstruction. Abdominal actinomycosis may spread to the abdominal wall, by means of sinus tract formation.

As far as the pelvic type of actinomycosis is concerned, it has been associated with the use of intrauterine contraceptive devices. Typical symptoms include pain in the lower part of the abdomen and sinus tracts which release discharge in the vagina.Thoracic actinomycosis involves symptomatology that closely resembles that of tuberculosis: thoracic pain, fever and sputum production with cough. Fistulas may also develop  

Thoracic actinomycosis involves symptomatology that closely resembles that of tuberculosis: thoracic pain, fever and sputum production with cough. Fistulas may also develop, connecting actinomyces colonies to the thoracic wall. Lastly, the generalized disease type involves infestation of various organs, such as the liver, skin, spinal cord, kidneys etc. Its manifestations depend upon which organ in infected each in each case. 


The diagnosis of actinomycosis can be achieved through cultures, histology and various imaging studies.


The first step toward a successful identification of the pathogen is a culture. Samples are obtained from sinus discharge material, abscess material or larger samples, if there is a need. The pathogen requires at least 2 weeks of culturing in order to develop [1]; the conditions should be anaeronic or minimally aerobic to allow for actinomyces to develop in a laboratory. A significant disadvantage of the culturing method that should always be kept in mind, is that actinomycosis is not tone of the first diagnoses that a physician considers when a patient present with the corresponding symptomatology. Therefore, patients who suffer from actinomycosis are very likely to have undergone various medication schemes prior to the culture, which could account fro a falsely negative culture, although an actinomycosis infection is present.


A diagnostic examination that can reliably diagnose actinomycosis is a histological examination of a sample, harvested from affected tissue. Findings such as neutrophilic infiltration, plasma cells, macrophages and lymphocytes further corroborate the existence of such an infection; the former usually encase fibrotic structures.

By far the most typical observation in a tissue sample infested by actinomycetes are the sulfur granules. They are small in size (100-1000 μm), contain a compound protein-polysaccharide and require calcium and phosphate for their mineralization, which the host themselves provide [11]. The term sulfur does not refer to the granules' composition; it is merely a reference to their typically sulfur-like color (yellow). This granulomatous appearance is typical for actinomycosis, it is not,however, pathognomonic, as other microorganisms, such as Nocardia brasiliensis amongst other, manifest in the same way in a histological examination. A definitive differential diagnosis between actinomycosis and infections occurring due to other pathogens can be achieved though immunohistology: the examination in question allows for an accurate identification via monoclonal antibodies stained with fluorescein.

Imaging studies

Finally, radiological depiction of affected areas could be helpful, as the physician can gain an insight of the morphology of the underlying lesions. Chest X-rays could depict a mass or pneumonitis, possibly with pleural involvement. Lesions are often depicted as non-defined masses with no accurately observed boundaries that can extend to various direction. A computed tomography (CT) scan, on the other hand, could depict a lesion that tends to extend to adjacent tissues with regions of diminished attenuation [12].


The most vital therapeutic measure in order to eradicate actinomycosis is a proper antibiotic scheme. Minimum eight weeks of treatment with penicillin G is required and doses should be high (3.000.000-5.000.000 units IV q 6 hours) [13]. Macrolides such as erythromycin and tetracyclines can also be used [14]. Sometimes therapy is administered for up to a year since the inadequate perfusion of the lesions does not allow for the full effect of the medications. Should another agent be identified in the sample examined, further antibiotics are introduced to the scheme, in order to cover all pathogens.

In cases of abdominal actinomycosis, treatment usually comprises amoxicillin and clavulanic acid accompanied by metronidazole, and an aminoglycoside for resistant Enterobacteriaceae.

Surgical intervention is not applied instead of medication, but simply aims at decompressing structures in cases of lesion-induced obstruction, at minimizing pathogen load by draining an abscess or at resecting a fistula.


Cervicofacial actinomycosis has the best prognosis, followed by the thoracic, abdominal and widespread type. Cases where the CNS displays signs of infection as well, exhibit the poorest prognosis. Generally, early and successful diagnosis and an appropriate therapeutic scheme are the best prognostic markers for each distinct type of actinomycosis.


Actinomyces, members of the greater family of Actinomycetaceae, are the bacteria responsible for causing actinomycosis. They constitute gram-positive bacteria of a thread-like morphology, which fail to produce spores [3].

The Actinomyces genus encompasses many bacterial species; the ones most frequently responsible for infection, however, are A. israeli, A. gerencseriae and A. turicensis [4]. These bacteria survive under anaerobic conditions or conditions with minimal oxygen supply and do not normally cause extensive tissue colonization. The occurrence of an Actinomyces infection is rendered possible by companion bacteria, such as A. acinomycetemcomitans, Prevotella and Bacteroides, which augment the virulence of Actinomyces.


The incidence of actinomycosis has significantly diminished in the industrialized world, due to the availability of antimicrobial treatment and better oral hygiene [5]. People of all ages are affected equally; it seems that men tend to be slightly more frequently affected than women (1.5:1 to 3:1) [6].

Sex distribution
Age distribution


Actinomycosis most commonly affects the neck, head and mouth (cervicofacial type) or the abdomen, approximately 60% of all actinomycosis patients suffering from the former and 15% of the latter. Actinomyces colonies located in the thorax or brain are very rarely seen [7].

The bacteria can infest tissue if there has been a loss of tissue continuity (traumatization) or already necrotic tissue. The infection initiates an extensive immunological response from the host; exterminated bacteria and dead tissue form pus-filled abscesses and granulomatous formations engulf actinomyces colonies in order to isolate them. Sometimes this acute immune response leads to fibrosis. Lastly, sinus tracts are displayed, which produce discharge when they break through the skin [8].

The infection is easily spread from the initial colonization region to adjacent locations via an injury or severer trauma. In the case of cervicofacial actinomycosis, traumatizations (orofaciomaxillary or other) results to the spreading of bacteria to nearby locations. Sinus tracts are formed as the infection progresses; discharge is observed as having a yellow color, closely resembling sulfur, and contains granules. Further actinomyces dissemination to the skull or blood volume is a rare observation and primarily occurs in neglected cases.


Some suggestions might include careful and meticulous dental hygiene and regular visits to the dentist. Women who use an intrauterine contraceptive device should be aware of the latter's association with pelvic actinomycosis


Actinomycosis is a result of infection with the bacterium Actinomyces israelii. The gram-positive bacterium is part of the natural flora of the oral cavity and tonsils; when it is dislocated, however, it infects tissue and leads to the formation of an abscess that manifests as a rigid, red or purple mass.

Depending on the location that the bacteria infest and the infestation pathway, actinomycosis is clinically divided into 5 distinct categories:

  • Cervicofacial actinomycosis: limited to the head, neck and mouth [1]. It is the most common type of the disease and occurs when the bacteria bypass the periodontal barrier and enter adjacent tissue, as is observed after tooth removal. Other infestation pathways include abrasions of tissue and salivary glands. Dental hygiene is believed to be of utmost importance in order to avoid actinomycosis.
  • Thoracic actinomycosis: affects the pulmonary parenchyma and mediastinum.
  • Pelvic actinomycosis: bacteria infest the female pelvic region [2].
  • Abdominal actinomycosis: it is usually a result of prior abdominal surgery, commonly for the treatment of appendicitis [1] or ulcer perforation. Actinomyces can disseminate and infest the abdominal walls as well.
  • Generalized actinomycosis: may affect multiple regions of the body, i.e hepatic, brain, skin or genital infestation.

Patient Information

Actinomycosis is an infection caused by a bacterium, Actinomyces israelii. This bacterium is normally found in the nasal cavities and throat and is part of the body's natural flora; this means that it coexists in those locations and causes no infections whatsoever.

However, in cases where tissue is injured, bacteria can disseminate to adjacent locations and cause a chronic infection, most commonly at the neck and mouth, and secondarily in the lungs, pelvis, abdomen, or in multiple organs at the same time. Actinomycosis cannot be transmitted from one person to another.

Typical symptomatology includes swollen lesions or masses of a purple/red color, tracts that discharge a yellowish substance and fever. The infection is diagnosed by a culture of the fluids discharged, with histological examinations (observed with a microscope) and a Computerized Tomography scan or an X-ray.

Treatment relies on a proper antibiotic combination. The actinomycetes bacteria are known to be sensitive to various antibiotics (tetracyclines, macrolides etc.) and these antibiotics should be taken for a long time, in order to completely eliminate any traces of actinomycosis. Sometimes, the culture detects another type of microorganism involved in the infection; in those cases, another antibiotic is added to cover for the additional pathogen. Surgical processes are reserved for occasions when the lesions are obstructing an organ, such as the intestines, or to relieve an abscess before it is treated with antibiotics.


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