Multiplication of Mycobacterium lepraemurium in mouse foot-pad cell culture.

Abstract

A limited multiplication of Mycobacterium lepraemurium was observed in cultures of mouse foot-pad cells up to the third sub-culture. After 96 hr of incubation at 33 C for phagocytosis, infected cells were washed to remove unphagocytized bacteria and transferred to new culture vessels. There was a 4.9-fold increase in the number of bacteria during 70 days of successive cultures up to the third culture in flasks, giving an overall generation time of 30.4 days. Acid-fast stained cover-slips taken from the culture in Leighton tubes revealed intracellular multiplication of M. lepraemurium, frequently in bundles of hundreds of bacteria, and gave an average generation time of 16.4 days in the primary, 15.7 days in the secondary, and 8.1 days in the tertiary culture. Elongation of M. lepraemurium was observed as early as 6 days after infection. All attempts to grow the acid-fast bacteria from the original bacillary suspension and the cell suspension at the end of the experiment on artificial culture media have failed. However, subcutaneous inoculations of these materials to mice produced the typical lesions caused by M. lepraemurium.