Of the chronic infections—malaria, syphilis, tuberculosis, and their like—leprosy still presents the greatest enigma. Mycobacterium leprae, reported by Hansen in 1874 and defined by Neisser in 1879, has not grown luxuriantly in laboratory cultures, yet some progress has been made. Rees and collaborators and Chang have developed successful, but different, techniques with M leprae murium, and some success with the leprosy bacillus has followed. Shepard had earlier discovered slow growth of the organism in foot-pads of mice, and lesions of similarly limited extent in hamsters have been seen by Waters and Niven, as well as strikingly in hamster nerves by Binford. The footpad lesions have been adequate to measure drug resistance to the effects of sulfones by organisms obtained from treated patients. Undoubtedly, these techniques will find further applications, as in the demonstration that foot-pad infection can be prevented by BCG vaccine.
If leprosy is a microbiological puzzle, it is