Periodicity of Sporadic Bacillemia in Experimental Tuberculosis in Dogs

Abstract

The author 1 has reported the occurrence of sporadic bacillemia in 17 of 20 dogs infected experimentally with virulent human tubercle bacilli (H 37). This report represents a further study of some factors in the time relationships of bacillemia in tuberculous dogs, including some of the animals included in the previous report.

Dogs were injected intravenously or subcutaneously with virulent human tubercle bacilli (H 37) in a suspension of Kaolan, mineral oil, and normal saline, the doses ranging from 3 to 20 mg. Femoral arterial punctures were performed daily on all dogs, and 3 to 5 cc of arterial blood withdrawn, under sterile precautions and injected directly into guinea pigs, usually subcutaneously in the right inguinal region. Endermal tuberculin tests were done on all guinea pigs before inoculation with the dogs' blood, and at intervals up to 3 months after inoculation, when all were sacrificed and necropsied.

The presence of tuberculosis was established on the basis of the characteristic pathology of injection—tuberculosis, supported by positive tuberculin reactions and microscopic examination of smears for tubercle bacilli.

All guinea pigs injected on 2 successive days were usually kept in the same cage during the 3-month period of observation. At necropsy it was noted that in some cages there was a high percentage of guinea pigs positive for tuberculosis while in other cages all were negative. The possibility that this might be due to spontaneous infection was considered. However, as Saenz et al. 2 have pointed out, spontaneous laboratory infection does not occur in less than 6 months' exposure, and the longest period of exposure to infection possible in this experiment was 3 months. Moreover, the anatomical distribution of the tuberculous lesions in our guinea pigs conformed closely to those described by Wilson 3 as typical of injection—tuberculosis i. c., inguinal glands and spleen chiefly involved, rarely liver, very rarely lungs or intestines.