Inoculation of Mice with Mycobacterium fortuitum into Foot-Pad

Abstract

Deformity of feet, such as shortening of fingers and absorption of phalanges, was observed in some mice of the dd strain which had been inoculated subcutaneously with Mycobacterium leprae into the foot-pad. In order to clarify the causation of this deformity, some species of Mycobacterium were injected into the food-pad of mice. As a result, the injection of a mixture of M. fortuitum and adjuvant induced the deformity, which gave rise to abscess formation and absorption of phalangeal bones, but that of a suspension of M. fortuitum in saline solution caused no deformity in mice. That deformity, however, was different from that observed in the deformed feet of mice inoculated with M. leprae. This particular finding would be used for the differentiation of M. fortuitum and M. runyonii from any other species of Mycobacterium.
No viable bacteria were seen in mice 6 weeks after the subcutaneous injection with a suspension of M. fortuitum in saline solution into the foot-pad, but killed bacteria were observed 2 years after the inoculation. Whether an organism was living or dead in the tissue of the foot-pad was determined by examining the form and length of the organism. The gathering and elongation of bacteria in living state could be observed in mice 20 weeks after the inoculation into the foot-pad.
Bacterial counting is only one important method for the detection of M. leprae trasmitted into the foot-pad of the mouse, because it is impossible to culture M. leprae in any medium. Therefore, the method developed in the present investigation for the differentiation of living bacteria from dead ones will be useful for the experiment on inoculation of mice with M. leprae into the foot-pad.