Actinomycetes are Gram-positive, branching higher bacteria (not fungi) and include Actinomyces israelii, Nocardia asteroides and N. brasiliensis. Actinomyces is a normal mouth and intestine commensal, but Nocardia is a soil saprophyte. Actinomyces produces an illness characterized by chronicity and poor infectivity. It has a worldwide distribution. Disease due to N. asteroides is frequently seen in the USA and Europe, whereas N. brasiliensis gives rise to disease more commonly in southern Asia.
In actinomycosis, characteristic clusters of organisms referred to as ‘sulphur granules’ are formed. Actinomyces is a rare cause of disease in the Western World. Three clinical forms of disease are recognized:
1 The cervicofacial variety usually occurs following dental extraction. It is often indolent and slowly progressive, associated with little pain, and results in induration and localized swelling of the lower part of the mandible (‘lumpy jaw’). Lymphadenopathy is uncommon. Occasionally acute inflammation occurs.
2 The thoracic variety follows inhalation of these organisms into a previously damaged lung. The clinical picture is not distinctive and is often mistaken for malignancy or tuberculosis. Symptoms such as fever, malaise, chest pain and haemoptysis are present. Empyema occurs in 25% of patients and local extension produces chest-wall sinuses with discharge of sulphur granules.
3 Abdominal actinomycosis most frequently affects the caecum. Characteristically, a hard indurated mass is felt in the right iliac fossa. Later, sinuses develop. The differential diagnosis includes malignancy, tuberculosis, Crohn’s disease and amoeboma. Pelvic actinomycosis appears to be increasing with wider use of intrauterine contraceptive devices.
Treatment involves surgery, and penicillin is the drug of choice. High-dose i.v. penicillin is given for 4-6 weeks followed by oral penicillin for some weeks after clinical resolution. Tetracyclines are also effective. Nocardiosis
Nocardia gives rise to two distinct clinical entities:
I Pulmonary disease presents with cough, fever, and haemoptysis. Pleural involvement and empyema may occur.
2 Mycetoma is the result of local invasion by Nocardia and presents as a painless swelling, usually on the sole of the foot (madura foot). The swelling of the affected part of the body continues inexorably. Nodules gradually appear from which purulent fluid containing characteristic ‘grains’ of the organisms are discharged. Systemic symptoms and regional lymphadenopathy are distinctly uncommon. Sinuses may occur several years after the onset of the first symptom. Mycetoma may also be produced by several other members of actinornycetes, including Actinomadura and Streptomyces. It is then referred to as an actinomycetoma. When caused by true fungi belonging to Eumycetes, e.g. Madurella mycetomi or Petriellidium boydii, it is referred to as eumycetoma. The clinical presentation, with the exception of differently coloured ‘grains’, is similar to that of mycetoma.
This is often difficult to establish, as Nocardia is not easily detected in sputum cultures or on histological section.
Treatment consists of adequate surgical drainage of the pus combined with prolonged chemotherapy. The drug of choice is sulphadiazine in doses of up to 9 g daily. Cotrimoxazole may also be used.