A gram‐positive, nonmotile, facultatively anaerobic, pleomorphic bacterium. It is commonly found in the soil but can also be found in dental plaque and the intestinal tract of mammals. It is typically a commensal bacterium.
Causative organism of human actinomycosis. Tissue growth occurs as colonies of Gram-positive myceUum 0.8 -1.0 jam thick, with the filaments interlaced at the centre and arranged radially at the periphery, where Gram-negative clubs (which may be weakly acid-fast) terminate the hyphae. The mycelium may degrade to rod forms. Saline-washed pus may exhibit yellow pinhead-sized ‘sulphur granules’ which are typical of actinomycosis. These pressed gently between a slide and coverslip will best show the morphology. Culture is anerobic or micro-aerophilic with added CO2 ; deep shake cultures are often used. There is no growth on Sabouraud’s agar.
A species that causes actinomycosis in humans. One clinical form is called lumpy jaw because of the characteristic appearance of the swollen jaw produced by the infection. Prolonged therapy with very high doses of penicillin G is required.