A total of 32 mice received 0.3 ml injections of light suspensions of Rothia dentocariosa in the right thigh. Ten mice served as controls. Histologic studies demonstrated abscess formation at all experimental sites with healing at day 35. Bacteriologic samples taken up to day 13 provided live cultures.Georg and Brownt created the genus Rothia in the family Actinomycetaceae, to accommodate an organism previously known as A ctinomyces dentocariosus,2 Nocardia dentocariosus,3 and N salivae.4 They called this organism Rothia dentocariosa. Its occurrence in the human mouth is well established.2-6 Laboratory identification and its presence in human material (blood, spinal fluid, and abscesses) has been demonstrated.7 However, the etiologic relationship of this organism to disease is not understood.Materials and Methods Rothia dentocariosa, isolated from a human carious tooth, was used in this study. The cultures were grown on Trypticase soy agar slants* and washed down with phosphate buffer (pH 7) to form a light suspension of live organisms. A total of 32 mice received 0.3 ml injections in the right thigh and ten mice, serving as controls, received 0.3 ml injections of sterile phosphate buffer. The mice were killed as follows: 4 hours postinjection, 24 hours postinjection, daily from the 3rd to 15th day, and then on days 30, 44, 58, 72, and 180. Histologic studies were made of the injection sites. Formalin-fixed tissues were sectioned and stained with hematoxylin and eosin. Brown-Brenn stain was used as a special bacteriologic indicator. Recovery of the organisms after death was made by placing blood, a section of tissue, or inoculum from the abscess exudate into thioglycolate broth. Subsequent platings were made until identification was positive.Results The histologic studies of tissue taken four hours postinjection showed inflammation at the injection site. At 24 hours, inflammation was accompanied by suppuration. Round cell infiltration was beginning by the 48th hour and the 72-hour specimen showed intense inflammation surrounding the many organisms. By the seventh day, partial encapsulation had occurred and on the tenth day the abscesses contained necrotic centers. Tissue taken from the mouse killed on the 12th day showed a well circumscribed abscess with a necrotic center. Rothia were recovered daily from the abscesses which were suppurating at the time of autopsy in all specimens through the 13-day specimen.No cultures were attempted after the abscess had encapsulated (day 14). The BrownBrenn stains of the tissue sections from days 14 and 15 demonstrated the presence of the organisms within the circumscribed abscesses. At this time there were fat-laden cells present and the abscesses were undergoing repair. Repair was still apparent in the 30-day specimen, but at the 35th day and later, healing was complete. These findings supported the gross autopsy findings. During the experimental period there was no sinus formation from the abscesses and suppuration as contained within the body of the muscle or in the tiss...
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