Separation of Mycobacterium leprae from contamination with armadillo-liver-derived "pigment" particles.

Mycobacterium leprae isolated from armadillo liver by the widely used IMMLEP protocol is sometimes contaminated with a particulate "pigment." This paper describes a simple, efficient, and rapid method for purifying large quantities of contaminated bacteria, which may readily be used as an additional step added at the end of the protocol when necessary. The process involves a discontinuous Percoll gradient and generates an essentially pure fraction containing greater than 90% of the original bacteria, and a fraction of "pigment" slightly contaminated with bacteria. Use of the system should release large additional numbers of pure M. leprae suitable for use in human vaccine trials.