Systemic Mycobacterium lepraemurium infection in mice: differences in doubling time in liver, spleen, and bone marrow, and a method for measuring the proportion of viable organisms in an inoculum.

Counts of acid-fast bacilli were made on homogenates of whole liver, whole spleen, and two femurs of CBA mice killed at various time intervals after intravenous infection with Mycobacterium lepraemurium. The growth curves so obtained showed that the bacillus multiplied faster in bone marrow than in liver or spleen. No evidence of redistribution during the early part of infection was obtained. The time of appearance of significant numbers of bacilli (10(7)) in the bone marrow was used to make estimates of viability of M. lepraemurium suspensions. Several applications of the techniques described are discussed.