Actinomycosis

It is a subacute or chronic infection due to Actinomyces israelii or one of several other species. The body's reaction tends to be granulomatous or suppurative. Haematogenous spread can occur to distant sites but lymphatic spread is uncommon.

Actinomyces are present in the normal oral flora and to a lesser extent in the lower gastrointestinal tract and female genital tract. It is not virulent and requires a break in the mucous membranes and devitalised tissue to invade deeper body structures and cause illness. It is often part of a mixed infection with several species of actinomyces and other bacteria.

Actinomyces infection is commonest between the ages of 25 and 50 with a male preponderance of 3:1.

• 50 to 70% of cases occur in the head and neck
• 15 to 20% are thoracic
• 10 to 20% are in the abdomen or pelvis.

Poor oral hygiene with dental decay is a risk factor as is previous abdominal surgery.

HIV does not seem to increase risk significantly.¹ Devitalisation of tissue is a risk as in malignancy of the head and neck that has received radiotherapy.²

Presentation will vary according to the site of infection.

Head and Neck

• There may have been dental surgery, trauma to the mouth, poor oral hygiene with dental decay or periodontal disease.
• Chewing is difficult if there is involvement of the muscles of mastication.

Examination may show some of the following:

• There are often nodular lesions at the angle of the jaw. They slowly increase in size and number to form sinuses that open onto the cheek or under the mandible.
• If the extruding pus is squeezed between 2 glass microscope slides it has a characteristic appearance like sulphur granules.
• Nodules are not tender except possibly in the early stages. Later they become hard.
• Multiple sinuses may occur with exacerbations and remissions.
• There is a red or blue discolouration of the skin over the lesion.
• Lymph nodes are not palpable.
• Trismus is present if the muscles of mastication are involved.
• Fever is variable.

Thorax

• Fever, dry or productive cough.
• Shortness of breath, chest pain or haemoptysis.
• Weight loss, fatigue, anorexia.

Examination may show:

• Cachexia may be apparent and abnormal breath sounds heard.
• Sinus tracts draining from the chest wall.

Abdomen

In the abdomen there has usually been previous abdominal surgery. Symptoms are non-specific and include:

• Low-grade fever.
• Weight loss.
• Fatigue.
• Change in bowel habits.
• Vague abdominal discomfort.
• Nausea.
• Vomiting.
• Sensation of a mass.

Examination may show:

• Evidence of previous abdominal surgery.
• Low-grade fever and cachexia may occur but are variable.
• There is a mass, most often in the right lower quadrant but less often in the left lower quadrant. It is firm to hard, not tender and often fixed to the underlying tissue.
• Sinus tracts with drainage from either the abdominal wall or the perianal region.

Pelvis

• In the pelvis there has usually been an IUCD fitted, especially an old plastic device that has been present many years. Infection with a first generation IUCD was very common but it is much rarer with copper containing devices or IUS. The fact that copper devices and IUS have to be changed every 5 years may be important.
• Lower abdominal discomfort, abnormal vaginal bleeding or discharge.

Examination:

• There will be an adnexal mass.

This depends upon the site but includes:

• Malignancy.
• Tuberculosis.
• Appendix abscess or other causes of abdominal masses.
• Crohn's disease.
• Diverticular disease.
• PID.

Blood Tests

• FBC may show anaemia and mild leukocytosis.
• ESR often is elevated.
• Blood chemistry is normal unless there is hepatic involvement in which case alkaline phosphatase will be raised.

Isolation of the Organism

• Specimens need to be from draining sinuses, deep needle aspiration, or biopsies. Swabs, sputum, and urine specimens do not give satisfactory results.
• Prompt transport to the laboratory, preferably in an anaerobic transport device, gives best results.
• A Gram-stained smear may show the typical beaded, branched, gram-positive filamentous rods.
• Cultures should be under anaerobic conditions and incubated for at least 48 hours but the isolation and identification of actinomycetes may take 2 to 3 weeks.
• Nucleic acid probes and polymerase chain reaction (PCR) methods are being developed for more rapid identification.
• The preliminary diagnosis of actinomycosis also can be made by examining sulphur granules. Granules should be crushed between 2 slides, stained with 1% methylene-blue solution, and examined microscopically for actinomycetes.
• A cervical smear may show actinomycete-like organisms (ALO), especially if an IUCD is in situ but unless there is clinical evidence of PID they are of no significance. ALOs with an IUS are even lower than with a copper IUCD.³

Imaging

• CXR may show a poorly defined mass, pneumonitis or a cavitating lesion with or without pleural involvement. Hilar lymph nodes are uncommon.
• The presence of a mass that extends across fissures or pleura, invades into the adjacent chest wall or thoracic vertebrae, or causes local destruction of the ribs or sternum suggests thoracic actinomycosis.
• CT scans of any site usually reveal an infiltrating mass with focal areas of decreased attenuation that enhance with contrast. The mass tends to invade surrounding tissues.

Histology

CT or ultrasound-guided fine-needle aspiration or biopsy can be used to obtain clinical material for diagnosis. Actinomycosis is characterized by a mixed suppurative and granulomatous inflammatory reaction, connective tissue proliferation, and the presence of sulphur granules. The granules are virtually pathognomonic.

Non-Drug

There are no specific restrictions or requirements. The finding of actinomyces on a cervical smear does not require treatment or removal of the IUCD^4,5 unless there are clinical features of disease.

Drugs

Penicillin is the drug of choice. Resistance is rare. High doses have to be given for prolonged courses. In those who are allergic to penicillin options include tetracyclines, erythromycin, doxycycline and clindamycin. However, response to tetracyclines and ciprofloxacin is poor and a beta lactam antibiotic, perhaps with beta lactamase inhibitors, should be the first choice.⁶

Parenteral therapy may be required for severe infection before changing to the oral route. A typical regime for an adult is:

• Penicillin G 12 to 24 megaunits IV for 7 to 14 days followed by Penicillin V 500mg qds for 6 to 12 months. The exact duration and route of treatment will depend upon the response of the individual.⁷

Surgical

Surgery may include incision and drainage of abscesses, excision of sinus tracts and fibrosis, decompression if required and relief of obstruction including possible compression of a ureter.

• Osteomyelitis of the mandible, ribs, and vertebrae
• Brain abscess, chronic meningitis, cranial, epidural, and subdural infection and spinal epidural infection.
• Endocarditis.
• Disseminated actinomycosis.
• Hepatic abscess can be difficult to diagnose.⁸
• Although actinomyces like organisms are common and usually unimportant with an IUCD in situ, if pelvic actinomyces does occur it is difficult and usually requires total abdominal hysterectomy with bilateral salpingo-oophorectomy.⁹ It often masquerades as pelvic malignancy.

• When actinomycosis is diagnosed early and treated with a suitable regime the prognosis is excellent.
• The more advanced and complicated forms require aggressive antibiotic treatment and surgery.
• The outcome can occasionally be fatal.

Actinomycosis is a rare disease that can be a clinical mimic. It is essential to be aware of the diagnosis^9,10,11,12 that can be quite difficult to make unless correct techniques are employed. Failure to consider the possibility and to make the diagnosis can lead to unnecessary surgery and delay in adequate treatment.