Site of Multiplication of Human Leprosy Bacilli inoculated into the Foot-pads of Mice

Abstract

THE evidence for the transmission and multiplication of human leprosy bacilli in the foot-pads of mice^1–3 was formally accepted by a special committee of the Eighth International Congress of Leprology in 1963 (ref. 4). Quantitative analyses have shown that the multiplication of Mycobacterium leprae is limited, is dependent on the size of the inoculum and is confined to the foot-pad. For example, inocula of 10⁴ Myco. leprae (counted as acid-fast bacilli) yield 10⁶ in 6–8 months, and although smaller inocula may eventually give the same yield, larger ones give no higher yields, and inocula of 10⁶ or more fail to multiply significantly. Once the bacterial population in the foot-pad has reached approximately 10⁶ it remains steady for many months although there is a gradual increase in the proportion of dead bacilli². Myco. leprae recovered from foot-pads can be passaged apparently indefinitely, their bacteriological characteristics remaining unchanged.