Commen salism in pathogenic anaerobic Actinomyces cultures.

Conversion of a ‘rough’ typical strain of Actinomyces israelii of human origin to a ‘smooth’ soft form more tolerant of oxygen was found to result from the physical trapping within the mycelium of a few alien and facultatively anaerobic cells. Such cells, which commonly proved to be staphylococci, were isolated in single cell culture by micromanipulative techniques and then grown aerobically. Their presence affected the morphology and oxygen tension requirements of the host. In successfully balanced mixtures the colonies appeared homogeneous anaerobically and failed to grow aerobically. The commensal organism could most readily be detected in a water/gel system in stoppered bottle cultures. Similar associations were obtained from a variety of morbid material, especially that of bovine origin. It is suggested that the descriptions given by various workers at different times of a smooth soft micro-aerophilic organism little given to branching may cover : (1) A. israelii and associates; or (2) a distinct organism earlier described under the name of A. bovis.