Actinomycosis

Actinomycosis is a chronic suppurative disease caused by anaerobic bacteria, Actinomycetes israelii.

The disease is conventionally included in mycology though the causative organism is filamentous bacteria and not true fungus.
The organisms are commensals in the oral cavity, alimentary tract and vagina.
The infection is always endogeneous in origin and not by person-toperson contact.
The organisms invade, proliferate and disseminate in favourable conditions like break in mucocutaneous continuity, some underlying disease etc.

Depending upon the anatomic location of lesions, actinomycosis is of 4 types:

Commonest form (60%)
Has the best prognosis.
The infection enters from tonsils, carious teeth, periodontal disease or trauma following tooth extraction.

The infection in the lungs is due to aspiration of the organism from oral cavity
Initially, the disease resembles pneumonia but subsequently the infection spreads to the whole of lung, pleura, ribs and vertebrae.

Common in appendix, caecum and liver.
The abdominal infection results from swallowing of organisms from oral cavity or extension from thoracic cavity.

Infection in the pelvis occurs as a complication of intrauterine contraceptive devices (IUCD’s).

The inflammatory reaction is a granuloma with central suppuration.
Formation of abscesses in the centre of lesions and at the periphery chronic inflammatory cells, giant cells and fibroblasts are seen.
Centre of each abscess contains the bacterial colony, ‘sulphur granule’, characterised by radiating filaments (hence previously known as ray fungus) with hyaline, eosinophilic, club-like ends representative of secreted immunoglobulins.
Bacterial stains reveal the organisms as gram-positive filaments, nonacidfast, which stain positively with Gomori’s methenamine silver (GMS) staining